研究者データベース

佐藤 威友(サトウ タケトモ)
量子集積エレクトロニクス研究センター
准教授

基本情報

所属

  • 量子集積エレクトロニクス研究センター

職名

  • 准教授

学位

  • 博士(工学)(北海道大学)

ホームページURL

ORCID ID

J-Global ID

研究キーワード

  • 窒化物半導体   電子デバイス   ウェットエッチング   電気化学   多孔質構造   機能性表面   光電変換   化学センサ   

研究分野

  • ものづくり技術(機械・電気電子・化学工学) / 電子デバイス、電子機器
  • ものづくり技術(機械・電気電子・化学工学) / 電気電子材料工学

職歴

  • 2004年04月 - 現在 北海道大学量子集積エレクトロニクス研究センター 准教授
  • 2001年10月 - 2004年03月 北海道大学大学院工学研究科 助手
  • 2001年04月 - 2001年09月 北海道大学量子集積エレクトロニクス研究センター 研究員

学歴

  • 1998年04月 - 2001年03月   北海道大学   工学研究科   電子情報工学専攻・博士後期課程
  • 1996年04月 - 1998年03月   北海道大学   工学研究科   電子情報工学専攻・修士課程
  • 1992年04月 - 1996年03月   北海道大学   工学部   電気工学科

所属学協会

  • 電気化学会   電子情報通信学会   応用物理学会   米国電気化学会   

研究活動情報

論文

  • Michihito Shimauchi, Kazuki Miwa, Masachika Toguchi, Taketomo SATO, Junichi Motohisa
    Applied Physics Express 2021年10月06日 [査読有り][通常論文]
  • Masachika Toguchi, Kazuki Miwa, Fumimasa Horikiri, Noboru Fukuhara, Yoshinobu Narita, Osamu Ichikawa, Ryota Isono, Takeshi Tanaka, Taketomo Sato
    Journal of Applied Physics 130 2 024501 - 024501 2021年07月14日 [査読有り][通常論文]
  • Tamotsu Hashizume, Ryota Ochi, Erika Maeda, Toshihide Nabatame, Koji Shiozaki, Taketomo Sato
    Proceedings of SPIE - The International Society for Optical Engineering 11686 2021年 
    We have investigated AlGaN/GaN high-electron mobility transistors (HEMTs) with a high κ gate dielectric using hafnium silicate (HfSiOx). The (HfO2)/(SiO2) laminate structure was deposited on the AlGaN surface by a plasma enhanced atomic layer deposition, followed by a post-deposition annealing at 800 °C. The HfSiOx-gate HEMT showed good transfer characteristics with a high transconductance expected from its κ value and a subthreshold swing of 71 mV/ decade. In addition, we observed excellent capacitance-voltage (C-V) characteristics with negligible frequency dispersion in the metal-oxide-semiconductor (MOS) HEMT diode. The detailed C-V analysis showed low state densities in the order of 1011 cm-2 eV-1 at the HfSiOx/AlGaN interface.
  • 伊藤滉朔, 小松祐斗, 渡久地政周, 井上暁喜, 三好実人, 佐藤威友
    応用物理学会春季学術講演会講演予稿集(CD-ROM) 68th 2020年11月23日 [査読無し][通常論文]
  • Taketomo Sato, Masachika Toguchi
    ECS Meeting Abstracts 2020年11月23日 [査読無し][招待有り]
  • Shinji Yamada, Kentaro Takeda, Masachika Toguchi, Hideki Sakurai, Toshiyuki Nakamura, Jun Suda, Tetsu Kachi, Taketomo Sato
    Applied Physics Express 13 10 106505 - 106505 2020年10月01日 [査読有り]
  • Ryota Ochi, Erika Maeda, Toshihide Nabatame, Koji Shiozaki, Taketomo Sato, Tamotsu Hashizume
    AIP Advances 10 6 065215 - 065215 2020年06月01日 [査読有り][通常論文]
  • Kazuki Miwa, Yuto Komatsu, Masachika Toguchi, Fumimasa Horikiri, Noboru Fukuhara, Yoshinobu Narita, Osamu Ichikawa, Ryota Isono, Takeshi Tanaka, Taketomo Sato
    Applied Physics Express 13 2 026508 - 026508 2020年02月01日 [査読有り]
  • Fumimasa Horikiri, Noboru Fukuhara, Masachika Toguchi, Kazuki Miwa, Yoshinobu Narita, Osamu Ichikawa, Ryota Isono, Takeshi Tanaka, Taketomo Sato
    CS MANTECH 2020 - 2020 International Conference on Compound Semiconductor Manufacturing Technology, Digest of Papers 127 - 130 2020年 
    Photoelectrochemical (PEC) etching is a promising technology for fabricating GaN devices with low damage. In the simple contactless PEC (CL-PEC) etching process that includes K2S2O8 in the electrolyte as an oxidizing agent, a sample is dipped into the electrolyte under UV irradiation. In this study, we applied CL-PEC to the gate-recess process of GaN HEMTs on an SiC substrate. The etching depth of the recess showed considerable reproducibility by the self-termination feature, and the residual AlGaN layer thickness was approximately 5 nm. The Schottky gate HEMTs with a recessed structure showed the normally off characteristics, and the Vthvalue was +0.4 V with a standard deviation of ±3.8 mV.
  • Fumimasa Horikiri, Noboru Fukuhara, Hiroshi Ohta, Naomi Asai, Yoshinobu Narita, Takehiro Yoshida, Tomoyoshi Mishima, Masachika Toguchi, Kazuki Miwa, Taketomo Sato
    IEEE Transactions on Semiconductor Manufacturing 32 4 489 - 495 2019年10月 [査読有り][通常論文]
  • Taketomo Sato, Masachika Toguchi, Yuto Komatsu, Keisuke Uemura
    IEEE Transactions on Semiconductor Manufacturing 32 4 483 - 488 2019年08月 [査読有り][通常論文]
  • Masachika Toguchi, Kazuki Miwa, Taketomo Sato
    Journal of The Electrochemical Society 166 12 H510 - H512 2019年07月 [査読有り][通常論文]
  • Electrodeless photo-assisted electrochemical etching of GaN using a H3PO4-based solution containing S2O82– ions
    Masachika Toguchi, Kazuki Miwa, Fumimasa Horikiri, Noboru Fukuhara, Yoshinobu Narita, Takehiro Yoshida, Taketomo Sato
    Applied Physics Express 12 066504-1 - 066504-4 2019年05月 [査読有り][通常論文]
  • Keisuke Uemura, Manato Deki, Yoshio Honda, Hiroshi Amano, Taketomo Sato
    Japanese Journal of Applied Physics 58 SC SCCD20-1 - SCCD20-6 2019年05月 [査読有り][通常論文]
  • Horikiri Fumimasa, Fukuhara Noboru, Ohta Hiroshi, Asai Naomi, Narita Yoshinobu, Yoshida Takehiro, Mishima Tomoyoshi, Toguchi Masachika, Miwa Kazuki, Sato Taketomo
    APPLIED PHYSICS EXPRESS 12 3 2019年03月01日 [査読有り][通常論文]
  • Matsumoto Satoru, Toguchi Masachika, Takeda Kentaro, Narita Tetsuo, Kachi Tetsu, Sato Taketomo
    JAPANESE JOURNAL OF APPLIED PHYSICS 57 12 2018年12月 [査読有り][通常論文]
  • 佐藤威友
    ケミカルエンジニヤリング 63 6 399‐405  2018年06月 [査読無し][招待有り]
  • 植村圭佑, 松本悟, 渡久地政周, 伊藤圭亮, 佐藤威友, 佐藤威友
    電子情報通信学会技術研究報告 117 331(ED2017 49-71) 23‐26  2017年11月23日 [査読無し][通常論文]
  • Yusuke Kumazaki, Keisuke Uemura, Taketomo Sato, Tamotsu Hashizume
    JOURNAL OF APPLIED PHYSICS 121 18 2017年05月 [査読有り][通常論文]
     
    The photocarrier-regulated electrochemical (PREC) process was developed for fabricating recessed-gate AlGaN/GaN high-electron-mobility transistors (HEMTs) for normally off operation. The PREC process is based on photo-assisted electrochemical etching using low-energy chemical reactions. The fundamental photo-electrochemical measurements on AlGaN/GaN heterostructures revealed that the photo-carriers generated in the top AlGaN layer caused homogeneous etching of AlGaN with a smooth surface, but those generated in the GaN layer underneath caused inhomogeneous etching that roughens the surface. The concept of the PREC process is to supply the photo-carriers generated only in the AlGaN layer by selecting proper conditions on light wavelength and voltage. The phenomenon of self-termination etching has been observed during the PREC process, where the etching depth was controlled by light intensity. The recessed-gate AlGaN/GaN HEMT fabricated with the PREC process showed positive threshold voltage and improvement in transconductance compared to planar-gate AlGaN/GaN HEMTs. Published by AIP Publishing.
  • Yusuke Kumazaki, Satoru Matsumoto, Taketomo Sato
    JOURNAL OF THE ELECTROCHEMICAL SOCIETY 164 7 II477 - II483 2017年 [査読有り][通常論文]
     
    A low-damaged wet process utilizing electrochemical (EC) etching and subsequent chemical etching has been developed for the fabrication of GaN porous structures. Superior controllability in depth and diameter could be obtained by achieving anisotropic nature of the vertical direction to the substrate by EC etching and horizontal direction by tetramethylammonium hydroxide (TMAH) etching, respectively. The optical and photoelectrochemical properties of GaN porous structures were very sensitive to the structural properties. Photoreflectance measurement revealed that porous sample had an effective refractive index that could be controlled by TMAH etching time. In photoelectrochemical measurement, the incident-photon-to-current conversion efficiency (IPCE) was dramatically enhanced to as high as 91% by the formation of porous structures. A series of experimental results were consistently explained by the change of thickness of pore wall and width of space charge region. (C) The Author(s) 2017. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.
  • 熊崎祐介, 植村圭佑, 佐藤威友
    電子情報通信学会技術研究報告 116 357(CPM2016 90-112) 45‐50  2016年12月05日 [査読無し][通常論文]
  • Yusuke Kumazaki, Zenji Yatabe, Taketomo Sato
    JAPANESE JOURNAL OF APPLIED PHYSICS 55 4 04EJ12  2016年04月 [査読有り][通常論文]
     
    We aimed to develop a photoassisted electrochemical etching process for the formation of GaN porous structures. Pore linearity and depth controllability were strongly affected by the anode voltage. In addition, the use of light with an energy below the band gap played an important role in controlling the pore diameter. Spectro-electrochemical measurements revealed that the high electric field induced at the GaN/electrolyte interface caused a redshift of the photoabsorption edge. This specific phenomenon can be explained by a theoretical calculation based on the Franz-Keldysh effect. On the basis of the results of our experimental and theoretical analyze, we propose a formation model for GaN porous structures. We also note that the application of the Franz-Keldysh effect is useful in controlling the structural properties of GaN porous structures. (C) 2016 The Japan Society of Applied Physics
  • Taketomo Sato, Xiaoyi Zhang, Keisuke Ito, Satoru Matsumoto, Yusuke Kumazaki
    2016 IEEE SENSORS 2016年 [査読有り][通常論文]
     
    The feasibility of liquid-phase sensors based on n-type GaN and n-type InP porous structures was investigated. The response currents to the addition of H2O2 increased on the porous electrodes. The source-drain currents of ion-sensitive field-effect transistors having a porous channel changed with good response to the pH values. The sensitivities of two kinds of chemical sensors to ions were drastically enhanced by the implementation of the porous structures having large surface areas with good conductivity.
  • Taketomo Sato, Yusuke Kumazaki, Masaaki Edamoto, Masamichi Akazawa, Tamotsu Hashizume
    GALLIUM NITRIDE MATERIALS AND DEVICES XI 9748 97480Y  2016年 [査読有り][招待有り]
     
    The selective and low-damaged etching of p-type GaN or AlGaN layer is inevitable process for AlGaN/GaN high-power transistors. We have investigated an electrochemical etching of p-GaN layer grown on AlGaN/GaN heterostructures, consisting of an anodic oxidation of p-GaN surface and a subsequent dissolution of the resulting oxide. The p- GaN layer was electrochemically etched by following the pattern of the SiO2 film that acted as an etching mask. Etching depth was linearly controlled by cycle number of triangular waveform at a rate of 25 nm/cycle. The AFM, TEM and mu-AES results showed that the top p- GaN layer was completely removed after 5 cycles applied, and the etching reaction was automatically sopped on the AlGaN surface. I-V and C-V measurements revealed that no significant damages were induced in the AlGaN/GaN heterostructures.
  • Taketomo Sato, Yusuke Kumazaki, Hirofumi Kida, Akio Watanabe, Zenji Yatabe, Soichiro Matsuda
    SEMICONDUCTOR SCIENCE AND TECHNOLOGY 31 1 2016年01月 [査読有り][通常論文]
     
    Photoresponse and photoabsorption properties of GaN porous structures were investigated by measuring photocurrent and spectroscopic photoabsorption under monochromatic light with various wavelengths. The measured photocurrents on the porous GaN electrodes were larger than those on the planar electrodes due to the unique features of the former electrode, such as large surface area and low photoreflectance properties. Moreover, the photocurrents were observed even under illumination with wavelength of 380 nm, corresponding to photon energy of 3.26 eV, which is 130 meV lower than the bandgap energy of bulk GaN. A potential simulation revealed that a high-electric field was induced at the pore tips due to modification of the potential in the porous structures. The observed redshift of the photoabsorption edge can be qualitatively explained by the Franz-Keldysh effect.
  • 喜田 弘文, 熊崎 祐介, 谷田部 然治, 佐藤 威友
    電子情報通信学会技術研究報告. ED, 電子デバイス 115 170 51 - 54 2015年07月 [査読無し][通常論文]
  • 熊崎 祐介, 渡部 晃生, 谷田部 然治, 佐藤 威友
    電子情報通信学会技術研究報告. ED, 電子デバイス 115 63 63 - 66 2015年05月 [査読無し][通常論文]
  • Zenji Yatabe, Joel T. Asubar, Taketomo Sato, Tamotsu Hashizume
    PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE 212 5 1075 - 1080 2015年05月 [査読有り][通常論文]
     
    We have investigated the effects of the inductively coupled plasma (ICP) etching of AlGaN surface on the resulting interface properties of the Al2O3/AlGaN/GaN structures. The experimentally measured capacitance-voltage (C-V) characteristics were compared with those calculated taking into account the interface states density at the Al2O3/AlGaN interface. As a complementary method, photoassisted C-V method utilizing photons with energies less than the bandgap of GaN was also used to probe the interface state density located near AlGaN midgap. It was found that the ICP etching of the AlGaN surface significantly increased the interface state density at the Al2O3/AlGaN interface. It is likely that ICP etching induced the interface roughness, disorder of chemical bonds and formation of various type of defect complexes including nitrogen-vacancy-related defects at the AlGaN surface, leading to poor C-V curve due to higher interface state density at the Al2O3/AlGaN interface.
  • Akio Watanabe, Yusuke Kumazaki, Zenji Yatabe, Taketomo Sato
    ECS ELECTROCHEMISTRY LETTERS 4 5 H11 - H13 2015年 [査読有り][通常論文]
     
    We investigated the structural features of gallium-nitride-porous structures formed using the photo-assisted electrochemical process in the back-side illumination (BSI) mode. The pore diameter and depth were strongly affected by the direction of illumination, where higher controllability was achieved compared with front-side illumination. The spectroscopic measurements revealed that illumination with photon energy below the bulk bandgap plays an important role in pore formation. We propose a formation model by considering the Franz-Keldysh effect that can consistently explain the obtained experimental data in which anodic etching occurs only at the pore tips under the high electric field induced in the depletion region. (C) 2015 The Electrochemical Society. All rights reserved.
  • Taketomo Sato, Hirofumi Kida, Yusuke Kumazaki, Zenji Yatabe
    ECS Transactions 69 2 161 - 166 2015年 [査読有り][通常論文]
     
    Photoabsorption properties of GaN porous structures were investigated by measuring photocurrent and light transmittance under monochromatic light with various wavelengths. The measured photocurrents on the porous GaN electrode were larger than those on the planar electrodes, and those were observed even under illumination with lower photon energy than the bandgap energy of bulk GaN. Moreover, the light transmittance that was measured in the back-side illumination (BSI) mode depended strongly on the applied voltage to the porous electrode with change of the photocurrents. The observed photoabsorption properties can be qualitatively explained by the Franz-Keldysh effect namely, the high electric field induced in the GaN porous structure easily causes a redshift of the photoabsorption edge.
  • Zenji Yatabe, Yujin Hori, Wan-Cheng Ma, Joel T. Asubar, Masamichi Akazawa, Taketomo Sato, Tamotsu Hashizume
    Japanese Journal of Applied Physics 53 10 100213-1 - 10 2014年10月 [査読有り][通常論文]
     
    <b>第38回(2016年度)応用物理学会優秀論文賞</b>

    <b>Spotlights 2014</b>

    <b>Selected Topics in Applied Physics, "Progresses and Future Prospects in Nitride Semiconductors"</b>

    This paper presents a systematic characterization of electronic states at insulators/(Al)GaN interfaces, particularly focusing on insulator/AlGaN/GaN structures. First, we review important results reported for GaN metal–insulator–semiconductor (MIS) structures. SiO<sub>2</sub> is an attractive material for MIS transistor applications due to its large bandgap and high chemical stability. In-situ SiNx is effective for improving the operation stability of high electron mobility transistors (HEMTs). Meanwhile, Al<sub>2</sub>O<sub>3</sub>/GaN structures have high band offsets and low interface state densities, which are also desirable for insulated gate applications. We have proposed a calculation method for describing capacitance–voltage (<i>C</i>–<i>V</i>) characteristics of HEMT MIS structures for evaluating electronic state properties at the insulator/AlGaN interfaces. To evaluate near-midgap states at insulator/AlGaN interfaces, a photo-assisted <i>C</i>–<i>V</i> technique using photon energies less than the bandgap of GaN has been developed. Using the calculation in conjunction with the photo-assisted <i>C</i>–<i>V</i> technique, we estimate interface state density distributions at the Al<sub>2</sub>O<sub>3</sub>/AlGaN interfaces.
  • Yusuke Kumazaki, Akio Watanabe, Zenji Yatabe, Taketomo Sato
    Journal of The Electrochemical Society 161 10 705 - 709 2014年08月 [査読有り][通常論文]
     
    We investigated the correlation between structural and photoelectrochemical properties of GaN porous nanostructures formed by photo-assisted electrochemical etching. The porous nanostructures were formed during light irradiation of the top-surface of homo-epitaxial layers grown on freestanding GaN substrates. The pore depth, wall thickness, and surface morphology of porous nanostructures were strongly influenced by the way holes generated by the light irradiation were supplied. Such structural features influenced the optical properties of GaN porous nanostructures. The photoluminescence peaks measured on GaN porous nanostructures were shifted to higher energies because of the quantum confinement in the thin GaN walls between pores. Formation of porous nanostructure decreased the photoreflectance of the GaN surface, and the smallest reflectance was obtained from the porous sample having large pores on its surface after the ultrathin layer with small pores had been removed by surface-etching. The photoelectrochemical response measured on GaN porous nanostructures in a NaCl electrolyte were drastically enhanced by the unique features of those structures, such as low photoreflectance and large surface area. The largest photocurrents were obtained from the sample from which H<sub>3</sub>PO<sub>4</sub> treatment had removed the ultrathin layer without thinning the pore walls.
  • 佐藤威友, 熊崎祐介, 渡部晃生
    表面技術協会講演大会講演要旨集 129th 295 - 297 2014年03月 [査読無し][招待有り]
  • 橋詰 保, 谷田部 然治, 佐藤 威友
    電気学会研究会資料. EDD, 電子デバイス研究会 EDD-14 39-49 13 - 16 2014年03月 [査読無し][招待有り]
  • 橋詰保, 谷田部然治, 佐藤威友
    表面科学 35 2 96-101 (J-STAGE) - 101 The Surface Science Society of Japan 2014年 [査読無し][招待有り]
     
    Interface properties of GaN-based heterostructures have been characterized. Schottky contacts on dry-etched n-GaN layers showed leaky I-V characteristics. An anneal process at 400°C was effective in recovering the rectifying characteristics. To characterize interface properties of Al2O3 insulated gates on AlGaN/GaN structures with and without the inductively coupled plasma (ICP) etching of AlGaN, we have developed a C-V calculation method taking into account electronic state charges at the Al2O3/AlGaN interface and a photoassisted C-V technique utilizing photons with energies less than the bandgap of AlGaN. It was found that the ICP etching caused the monolayer-level interface roughness, disorder of the chemical bonds and formation of various types of defect complexes at the AlGaN surface, resulting in poor C-V characteristics due to high-density interface states at the Al2O3/AlGaN interface.
  • 熊崎祐介, 渡部晃生, 谷田部然治, 佐藤威友
    電子情報通信学会技術研究報告 113 329(ED2013 64-89) 113 - 116 2013年11月 [査読無し][通常論文]
  • Yusuke Kumazaki, Tomohito Kudo, Zenji Yatabe, Taketomo Sato
    Applied Surface Science 279 116 - 120 2013年08月15日 [査読有り][通常論文]
     
    We investigated the optical absorption properties of InP porous structures formed by the electrochemical process using photoelectric conversion (PC) devices formed on p-n junction substrates. The photocurrent measurements revealed that the current from PC devices changed in response to the incident light power and the thickness of the top layer on the p-n interface. Since the photocarriers contributing to the observed photocurrents are excited by the photons reaching the p-n interface through the top layer, the photocurrents give us information on the optical absorption properties of the top layer. The photocurrents observed on a porous device with a porous structure in the top layer were lower than that of a non-porous device, indicating that the absorption properties of InP were enhanced after the formation of porous structures. This phenomenon can be explained in terms of absorption coefficient, α, increased by the light scattering and the sub-bandgap absorption in the porous layer. © 2013 Published by Elsevier B.V.
  • 気化学的手法によるInP多孔質構造の光吸収特性と光電変換
    熊崎 祐介, 神保 亮平, 谷田部 然治, 佐藤 威友
    電子情報通信学会技術研究報告 113 39(ED2013-27) 61 - 64 2013年05月 [査読無し][通常論文]
  • 電気化学的手法によるInP多孔質構造の光吸収特性と光電変換
    熊崎 祐介, 神保 亮平, 谷田部 然治, 佐藤 威友
    電子情報通信学会技術研究報告 113 39(ED2013-27) 61 - 64 2013年05月 [査読無し][通常論文]
  • Ryohei Jinbo, Yusuke Kumazaki, Zenji Yatabe, Taketomo Sato
    ECS Transactions 50 37 247 - 252 2013年03月 [査読有り][通常論文]
     
    Schottky interfaces were formed on InP porous structures by the electrodeposition of Pt films. The coverage of the Pt film and its optical reflectance depended largely on the surface morphology of the porous structure. Removal of the irregular top layer formed at the initial stage of the pore formation effectively improved the coverage of the Pt film inside pores. According to <i>I</i>-<i>V</i> measurements, the Pt/porous InP showed higher photocurrents with lower dark currents than those of a reference planar sample.
  • Yujin Hori, Taketomo Sato, Tamotsu Hashizume
    2013 1ST IEEE WORKSHOP ON WIDE BANDGAP POWER DEVICES AND APPLICATIONS (WIPDA) 143 - 146 2013年 [査読有り][通常論文]
     
    Interface properties of Al2O3 insulated gates on AlGaN/GaN structures prepared by atomic layer deposition have been characterized, focusing on the interface state density distribution at the Al2O3/AlGaN interface. We have developed a C-V calculation method taking into account electronic states charges at the Al2O3/AlGaN interface and a photoassisted C-V technique utilizing photons with energies less than the bandgap of AlGaN. These techniques were then applied to investigate the effect of the ICP etching of AlGaN on the interface properties.
  • Ryohei Jinbo, Tomohito Kudo, Zenji Yatabe, Taketomo Sato
    THIN SOLID FILMS 520 17 5710 - 5714 2012年06月 [査読有り][通常論文]
     
    A photoelectric-conversion device-based on an InP porous structure utilizing the large surface area inside pores and the low reflectance on the porous surface-is proposed. The InP walls inside the pores are covered with thin platinum films that form a Schottky barrier yielding an electric field that separates photo carriers generated under illumination. The coverage of the platinum film and its optical reflectance depended largely on the surface morphology of the porous structure. Removal of the irregular top layer formed at the initial stage of the pore formation effectively improved the coverage of the platinum film, which showed a very low optical reflectance (i.e., below 3.2%). According to current-voltage measurements under illumination, the platinum/porous InP showed larger photocurrents and higher responsivity than those of a reference planar sample. (C) 2012 Elsevier B.V. All rights reserved.
  • OKAZAKI Hiroyuki, SATO Taketomo, HASHIZUME Tamotsu
    電子情報通信学会技術研究報告. SDM, シリコン材料・デバイス 110 110 85 - 89 2010年06月23日 [査読無し][通常論文]
     
    We report the electrochemical formation of porous structures on n-type epitaxial layers grown on p-type InP substrates in view of the application to the photoelectric conversion devices. We successfully formed the arrays of regular-sized pores whose diameter and depth could be changed by the doping density and anodic conditions, respectively. From the photo I-V measurements, we confirmed the optical absorption process in the porous layers whose photovoltaic response strongly depended on the structural properties.
  • Taketomo Sato, Naoki Yoshizawa, Tamotsu Hashizume
    THIN SOLID FILMS 518 15 4399 - 4402 2010年05月 [査読有り][通常論文]
     
    Extremely low reflectance was obtained from InP porous nanostructures in UV, visible, and near-infrared ranges. Porous samples were electrochemically prepared on which 130-nm-diameter nanopores were formed in a straight, vertical direction and were laterally separated by 50-nm-thick InP nanowalls. The reflectance strongly depended on the surface morphology. The lowest reflectance of 0.1% in the visible light range was obtained after the irregular top layer had been completely removed. Superior photoelectrochemical properties were obtained on the InP porous structures clue to two unique features: the large surface area inside pores, and the large photon absorption enhanced on the low reflectance surface. (C) 2010 Elsevier B.V. All rights reserved.
  • T. Sato, N. Yoshizawa, H. Okazaki, T. Hashizume
    SEMICONDUCTOR ELECTROLYTE INTERFACE AND PHOTOELECTROCHEMISTRY 25 42 83 - 88 2010年 [査読有り][通常論文]
     
    Extremely low reflectance was obtained from InP porous nanostructures in UV, visible, and near-infrared light ranges. The reflectance strongly depended on the surface morphology of the porous structures prepared by the electrochemical process, and the lowest reflectance of 0.1% in the visible light range was obtained from a sample after the irregular top layer was completely removed. Large anodic photocurrents were obtained on the InP porous structures that had low reflectance surfaces with deeper pores.
  • Taketomo Sato, Akinori Mizohata, Tamotsu Hashizume
    JOURNAL OF THE ELECTROCHEMICAL SOCIETY 157 2 H165 - H169 2010年 [査読有り][通常論文]
     
    The electrochemical functionalization of n-type InP porous nanostructures and their feasibility for biochemical sensor applications were investigated. The porous structures have extremely large surface areas, i.e., over 10 m(2)/cm(3), and superior electrical properties with conductive semiconductor substrates. As a first attempt at electrochemical functionalization, we successfully deposited a glucose oxidase (GOD) membrane onto an InP surface under an applied anodic bias of 1.2 V. With the addition of glucose, the response currents on the porous electrodes increased compared to those on planar InP electrodes due to their enlarged surface area. The sensitivity curves of the porous electrodes we used showed good linearity between the response currents and concentrations in a range from 0 to 5 mM.
  • 電気化学的手法によるInP多孔質構造の形成と高感度化学センサへの応用
    佐藤威友, 吉澤直樹, 岡崎拓行, 橋詰 保
    電子情報通信学会技術研究報告. ED, 電子デバイス ED2010 35 11 - 15 2010年 [査読無し][通常論文]
  • Hiroyuki Okazaki, Taketomo Sato, Naoki Yoshizawa, Tamotsu Hashizume
    2010 22ND INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE AND RELATED MATERIALS (IPRM) 2010年 [査読有り][通常論文]
     
    We demonstrated to form InP porous structures on n-type epitaxial layers grown on p-type (001) substrates. The high-density array of straight pores with 150nm diameter and 5000nm depth was formed by the electrochemical anodization process, where the pore depth could be controlled by the anodization time in the n-type layer. The present p-n InP porous structures show the low optical reflectance in UV-, visible-and near-infrared region. The current transport properties clearly show the rectifying behavior. These features are very promising for practical application to high-efficiency photo-sensitive devices.
  • Naoki Yoshizawa, Taketomo Sato, Tamotsu Hashizume
    JAPANESE JOURNAL OF APPLIED PHYSICS 48 9 91102  2009年09月 [査読有り][通常論文]
     
    We prove with this paper that InP-based open-gate field-effect transistors (FETs) work well as liquid-phase chemical sensors. The open-gate FET clearly exhibited current saturation and a pinch-off behavior in the electrolyte, resulting in a rapid response to the gate bias applied via the electrolyte. A series of sensing measurements showed that the surface potential of the InP linearly changed with the pH values of the electrolytes in a pH range from 3.0 to 12.0. The pH sensitivity of the open-gate FETs depended on the ion species contained in the electrolyte. A Si3N4 layer was useful as an ion selective membrane for the InP open-gate FETs to improve the selectivity of H+ ions. (C) 2009 The Japan Society of Applied Physics
  • 有田 正志, 菅原 陽, 植村 哲也, 足立 智, 菅原 広剛, 葛西 誠也, 松田 健一, 佐藤 威友, 高橋 庸夫, 福井 孝志
    応用物理教育 33 1 25 - 30 2009年07月31日 [査読無し][通常論文]
  • John Tolle, Radek Roucka, Brandon Forrest, Andrew V. G. Chizmeshya, John Kouvetakis, Vijay R. D'Costa, Christian D. Poweleit, Michael Groenert, Taketomo Sato, Jose Menendez
    CHEMISTRY OF MATERIALS 21 14 3143 - 3152 2009年07月 [査読有り][通常論文]
     
    This work describes the development and application of a new class of highly versatile Ge-Sn/Si (100) hybrid substrate systems for the integration of a broad range of technologically important II-VI optical materials on silicon platforms. GeSn buffer layers were grown directly on Si(100), via introduction of Lomer edge dislocations at the interface, and exhibited low densities of threading defects, atomically flat surfaces, and strain-free microstructures. Specialized cleaning protocols were first developed to obtain GeSn surfaces possessing superior chemical purity and single-crystalline, long-range orientation for subsequent heteroepitaxy. The quality of the resulting platforms was then validated using proof-of-concept fabrication of prototype AlGaAs/GaAs/AlGaAs quantum well structures, which exhibited optical properties comparable to those of analogs grown via homoepitaxy on bulk GaAs substrates. The application of these platforms in CMOS-compatible integration of the II-VI materials was explored using a progressive strategy based on the systematic epitaxial fabrication of simple binaries within Zn-Cd-Te-Se class. This culminated in the Formation of fully lattice matched ZnSc/'GeSn/Si(100) structures for the first time, as well as highly mismatched CdTe and CdTe/ZnTe systems directly on silicon. These successful depositions represent an important milestone en route to the ultimate integration of ZnSe, CdTe, Zn(1-)zCd(z)Te and Hg(1-x)Cd(x)Te with Si for applications in high-performance IR photodetectors, imaging technologies, and high-efficiency, low-cost solar cells.
  • SATO Taketomo, YOSHIZAWA Naoki, OKAZAKI Hiroyuki, HASHIZUME Tamotsu
    電子情報通信学会技術研究報告. ED, 電子デバイス 109 97 117 - 120 2009年06月17日 [査読無し][通常論文]
     
    We demonstrated to form InP porous structures on n-type epitaxial layers grown on p-type (001) substrates. The high-density array of straight pores with 150nm diameter and 5000nm depth was formed by the electrochemical anodization process, where the pore depth could be controlled by the anodization time in the n-type layer. The present p-n InP porous structures show the low optical reflectance in UV-, visible- and near-infrared region. The current transport properties clearly show the rectifying behavior. These features are very promising for practical application to high-efficiency photo-s...
  • SATO Taketomo, YOSHIZAWA Naoki, OKAZAKI Hiroyuki, HASHIZUME Tamotsu
    電子情報通信学会技術研究報告. SDM, シリコン材料・デバイス 109 98 117 - 120 2009年06月17日 [査読無し][通常論文]
     
    We demonstrated to form InP porous structures on n-type epitaxial layers grown on p-type (001) substrates. The high-density array of straight pores with 150nm diameter and 5000nm depth was formed by the electrochemical anodization process, where the pore depth could be controlled by the anodization time in the n-type layer. The present p-n InP porous structures show the low optical reflectance in UV-, visible- and near-infrared region. The current transport properties clearly show the rectifying behavior. These features are very promising for practical application to high-efficiency photo-s...
  • MIZOHATA Akinori, YOSHIZAWA Naoki, SATO Taketomo, HASHIZUME Tamotsu
    電子情報通信学会技術研究報告. SDM, シリコン材料・デバイス 108 122 327 - 330 2008年07月02日 [査読無し][通常論文]
     
    We investigated the electrocatalytic activity of n-type InP porous nanostructures and the feasibility of their functionalization for the biochemical sensor applications. The porous structures have extremely large surface areas over 10m^2/cm^3 and superior electrical properties with conductive semiconductor substrates. The response currents to the addition of H_2O_2 increased on the porous electrodes due to their enlarged surface area, and its sensitivity had good linearity with H_20_2 concentration. As a first attempt of the electrochemical functionalization, glucose oxidase membrane was su...
  • MIZOHATA Akinori, YOSHIZAWA Naoki, SATO Taketomo, HASHIZUME Tamotsu
    電子情報通信学会技術研究報告. ED, 電子デバイス 108 121 327 - 330 2008年07月02日 [査読無し][通常論文]
     
    We investigated the electrocatalytic activity of n-type InP porous nanostructures and the feasibility of their functionalization for the biochemical sensor applications. The porous structures have extremely large surface areas over 10m^2/cm^3 and superior electrical properties with conductive semiconductor substrates. The response currents to the addition of H_2O_2 increased on the porous electrodes due to their enlarged surface area, and its sensitivity had good linearity with H_20_2 concentration. As a first attempt of the electrochemical functionalization, glucose oxidase membrane was su...
  • Taketomo Sato, Akinori Mizohata, Naoki Yoshizawa, Tamotsu Hashizume
    APPLIED PHYSICS EXPRESS 1 5 51202  2008年05月 [査読有り][通常論文]
     
    The electrocatalytic activity of n-type InP porous nanostructures was investigated in terms of their application to amperometric biochemical sensors. The current sensitivities for H(2)O(2) detection were strongly dependent on the structural properties of these porous nanostructures. A sample with deeper pores responsed more sensitively because of the enlarged surface area inside the nanopores. The removal of an irregular top layer also effectively improved the current sensitivity. The conductive porous nanostructures presented here were very promising for the direct amperometric detection of H(2)O(2). (c) 2008 The Japan Society of Applied Physics.
  • Taketomo Sato, Akinori Mizohata
    ELECTROCHEMICAL AND SOLID STATE LETTERS 11 5 H111 - H113 2008年 [査読有り][通常論文]
     
    A photoelectrochemical (PEC) process was developed to remove the irregular top layer from InP porous nanostructures. After anodic formation of a nanopore array, the PEC process repeated in the same electrolyte under illumination. The etching rate of the pore surfaces was strongly associated with their structural properties, being greater in the irregular top layer. The irregular top layer was completely removed by monitoring and controlling the anodic photocurrents in the ramped bias mode. (c) 2008 The Electrochemical Society.
  • Taketomo Sato, Akinori Mizohata, Toshiyuki Fujino, Tamotsu Hashizume
    PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 5, NO 11 2008 5 11 3475 - 3478 2008年 [査読有り][通常論文]
     
    In this paper, we report the electrochemical formation of the InP porous nanostructures and their feasibility for the application to the amprometric chemical sensors. Our two step electrochemical process consists of the pore formation on a (001) n-type InP substrate and the subsequent etching of pore walls caused by changing the polarity of the InP electrode in A HCL based electrolyte. By applying the anodic bras to the Inp electrode, the high density array of uniform nanopores was formed on the surface Next, the cathodic bias was applied to the porous sample to reduce the wait thickness by cathodic decomposition of InP, where the thickness of InP nanowall decreased uniformly along the entire depth of the porous layer. From the amperometric measurements of the porous electrode, it was found that the electrocatalytic, activity was much higher than that of the planar electrode. Furthermore, the current sensitivity for the H(2)O(2) detection was much enhanced after the cathodic decomposition process. The InP porous nanostructure formed by the present process is one of the promising structures for the application to the semiconductor based bio/chemical sensors. (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  • Taketomo Sato, Akinori Mizohata, Naoki Yoshizawa, Tamotsu Hashizume
    ECS Transactions 16 3 405 - 410 2008年 [査読有り][通常論文]
     
    The photo-electrochemical (PEC) process was developed to remove the irregular top layer of InP porous nanostructures for the application to amperometric chemical sensors. The PEC etching rate of the pore surface was associated with their structural properties, resulting in the complete removal of the irregular layer by monitoring and controlling the anodic photo-currents. The porous electrode prepared by PEC process gave higher sensitivity for detecting H2O2 due to the enlarged openings of all pores with complete removal of irregular top layer. ©The Electrochemical Society.
  • Taketomo Sato, Akinori Mizohata, Toshiyuki Fujino, Tamotsu Hashizume
    Physica Status Solidi (C) Current Topics in Solid State Physics 5 11 3475 - 3478 2008年 [査読有り][通常論文]
     
    In this paper, we report the electrochemical formation of the InP porous nanostructures and their feasibility for the application to the amperometric chemical sensors. Our two step electrochemical process consists of the pore formation on a (001) n-type InP substrate and the subsequent etching of pore walls caused by changing the polarity of the InP electrode in a HCl-based electrolyte. By applying the anodic bias to the InP electrode, the high-density array of uniform nanopores was formed on the surface. Next, the cathodic bias was applied to the porous sample to reduce the wall thickness by cathodic decomposition of InP, where the thickness of InP nanowall decreased uniformly along the entire depth of the porous layer. From the amperometric measurements of the porous electrode, it was found that the electrocatalytic activity was much higher than that of the planar electrode. Furthermore, the current sensitivity for the H2O2 detection was much enhanced after the cathodic decomposition process. The InP porous nanostructure formed by the present process is one of the promising structures for the application to the semiconductor-based bio/chemical sensors. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.
  • Naoki Yoshizawa, Taketomo Sato, Akinori Mizohata
    Proceedings of IEEE Sensors 1305 - 1308 2008年 [査読有り][通常論文]
     
    In this paper, we demonstrated that the InP-based open-gate FET worked well as a liquid-phase chemical sensor in acid electrolytes. The open-gate FET clearly exhibited current saturation and pinch-off behavior in the electrolyte, resulted in a rapid response to the gate bias applied via the electrolyte. A series of sensing measurements showed that the surface potential of the InP linearly changed with the pH values of the electrolytes, and their sensitivity was strongly dependent on ion species contained in the electrolyte. © 2008 IEEE.
  • 佐藤威友
    村田学術振興財団年報 21 222 - 229 2007年12月 [査読無し][通常論文]
  • 塩崎奈々子, 石川史太郎, TRAMPERT A, GRAHN H. T, 佐藤威友, 橋詰保
    応用物理学会学術講演会講演予稿集 68th 3 1431  2007年09月04日 [査読無し][通常論文]
  • Toshiyuki Fujino, Taketomo Sato, Tamotsu Hashizume
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 46 7A 4375 - 4380 2007年07月 [査読有り][通常論文]
     
    A high-densjty array of size-controlled porous nanostructures was formed on InP(001) substrates by a two-step electrochemical process using anodic and cathodic reactions. After the formation of InP porous structures by anodization, we subsequently applied cathodic decomposition to the reduction of the lateral thickness of the InP pore wall. The etching rate of the pore wall was extremely low and strongly dependent on the cathodic bias and crystal orientations of the wall surface. The thickness of InP walls could be precisely controlled in the range of 15-30nm by changing cathodic bias and cathodic decomposition time. From the PL measurement at room temperature, the porous structures showed strong blue-shifted emissions due to quantum confinement in thinner InP nanowalls.
  • Nanako Shiozaki, Taketomo Sato, Tamotsu Hashizume
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 46 4A 1471 - 1473 2007年04月 [査読有り][通常論文]
     
    In this paper, we report on the feasibility of oxidizing n-GaN by an electrochemical process in a mixture containing an aqueous solution of tartaric a id and propylene glycol. Photons generated by UV illumination were supplied at the electrolyte-GaN interface during the oxidation process. In the constant-voltage mode, X-ray photoelectron spectroscopy analysis revealed that relatively thick Ga oxide layer formed on the n-GaN surface. However, the oxide surface was very rough. In addition, we found metallic Ga components in the oxide layer or at the oxide-GaN interface for longer oxidation times. On the other hand, a thin Ga2O3 layer with a smooth surface was grown by a constant-current process.
  • Taketomo Sato, Toshiyuki Fujino, Tamotsu Hashizume
    ELECTROCHEMICAL AND SOLID STATE LETTERS 10 5 H153 - H155 2007年 [査読有り][通常論文]
     
    A two-step electrochemical process using anodic and cathodic reactions was developed to form size-controlled nanostructures on InP(001) substrates. After anodic formation of a nanopore array, the cathodic decomposition process was applied to reduce the thickness of InP nanowalls. The etching rate of the nanowalls was extremely small and strongly dependent on the cathodic bias and crystal orientations of the wall surface. Wall thickness could be controlled in the range of 10-30 nm by changing the cathodic bias and processing time. (c) 2007 The Electrochemical Society.
  • KOKAWA Takuya, SATO Taketomo, HASHIZUME Tamotsu
    Extended abstracts of the ... Conference on Solid State Devices and Materials 2006 326 - 327 2006年09月13日 [査読無し][通常論文]
  • FUJINO Toshiyuki, SATO Taketomo, HASHIZUME Tamotsu
    Extended abstracts of the ... Conference on Solid State Devices and Materials 2006 728 - 729 2006年09月13日 [査読無し][通常論文]
  • Sato Taketomo, Oikawa Takeshi, Hasegawa Hideki, Hashizume Tamotsu
    Journal of Vacuum Science & Technology B Microelectronics and Nanometer Structures 24 4 2087 - 2092 2006年07月26日 [査読有り][通常論文]
     
    Fundamental growth properties were investigated for the size-controlled selective MBE growth of AlGaN/GaN nanowires on the GaN (0001) prepatterned substrates both experimentally and theoretically. The lateral size of the present GaN nanowire was determined by two facet boundaries formed within AlGaN barrier layers. From the series of wire growth experiments, the growth selectivity and the measured angle of the facet boundary strongly depended on the Al composition and the initial crystalline facets of the mesa patterned templates. The experimental evolution of the cross-sectional structures...
  • Takuya Kokawa, Taketomo Sato, Hideki Hasegawa, Tamotsu Hashizume
    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 24 4 1972 - 1976 2006年07月 [査読有り][通常論文]
     
    Liquid-phase sensing characteristics of open-gate AlGaN/GaN high electron mobility transistor (HEMT) structures were investigated in aqueous solutions and polar liquids. In de-ionized water, the open-gate HEMT clearly showed good drain I-V characteristics with current saturation and pinch-off behavior, very similar to I-V characteristics of typical Schottky-gate HEMTs. We observed a fine parallel shift in the transfer curves according to change in the pH value in a solution, indicating the corresponding potential change at the AlGaN surface. The sensitivity for the potential change was 57.5 mV/pH, very close to the theoretical value of 58.9 mV/pH at 24 degrees C for the Nernstian response to, H+ ions. In the low drain bias region, the drain current linearly decreased with the pH value. This also indicated a systematic potential change at the AlGaN surface due to pH change. The present open-gate device showed a fast response to the pH change and a stable operation at fixed pH values. A possible mechanism for the pH response of the AlGaN surface is discussed in terms of equilibrium reactions of hydroxyls at the AlGaN surface with H+ in a solution. It was also found that the device was quite sensitive to changes in the electrostatic boundary conditions of the open-gate area by exposure to polar liquids. The drain current linearly decreased with increasing normalized liquid dipole moment. (c) 2006 American Vacuum Society.
  • Hideki Hasegawa, Seiya Kasai, Taketomo Sato, Tamotsu Hashizume
    IEICE TRANSACTIONS ON ELECTRONICS E89C 7 874 - 882 2006年07月 [査読有り][招待有り]
     
    With advent of the ubiquitous network era and due to recent progress of III-V nanotechnology, the present III-V heterostructure microelectronics will turn into what one might call III-V heterostructure nanoelectronics, and may open up a new future in much wider application areas than today, combining information technology, nanotechnology and biotechnology. Instead of the traditional top-down approach, new III-V heterostructure nanoelectronics will be formed on nanostructure networks formed by combination of top-down and bottom-up approaches. In addition to communication devices, emerging devices include high speed digital LSIs, various sensors, various smart-chips, quantum LSIs and quantum computation devices covering varieties of application areas. Ultra-low power quantum LSIs may become brains of smart chips and other nanospace systems. Achievements of new functions and higher performances and their on chip integration are key issues. Key processing issue remains to be understanding and control of nanostructure surfaces and interfaces in atomic scale.
  • Hideki Hasegawa, Seiya Kasai, Taketomo Sato, Tamotsu Hashizume
    IEICE TRANSACTIONS ON ELECTRONICS E89C 7 874 - 882 2006年07月 [査読有り][招待有り]
     
    With advent of the ubiquitous network era and due to recent progress of III-V nanotechnology, the present III-V heterostructure microelectronics will turn into what one might call III-V heterostructure nanoelectronics, and may open up a new future in much wider application areas than today, combining information technology, nanotechnology and biotechnology. Instead of the traditional top-down approach, new III-V heterostructure nanoelectronics will be formed on nanostructure networks formed by combination of top-down and bottom-up approaches. In addition to communication devices, emerging devices include high speed digital LSIs, various sensors, various smart-chips, quantum LSIs and quantum computation devices covering varieties of application areas. Ultra-low power quantum LSIs may become brains of smart chips and other nanospace systems. Achievements of new functions and higher performances and their on chip integration are key issues. Key processing issue remains to be understanding and control of nanostructure surfaces and interfaces in atomic scale.
  • Taketomo Sato, Takeshi Oikawa, Hideki Hasegawa, Tamotsu Hashizume
    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 24 4 2087 - 2092 2006年07月 [査読有り][通常論文]
     
    Fundamental growth properties were investigated for the size-controlled selective MBE growth of AlGaN/GaN nanowires on the GaN (0001) prepatterned substrates both experimentally and theoretically. The lateral size of the present GaN nanowire was determined by two facet boundaries formed within AlGaN barrier layers. From the series of wire growth experiments, the growth selectivity and the measured angle of the facet boundary strongly depended on the Al composition and the initial crystalline facets of the mesa patterned templates. The experimental evolution of the cross-sectional structures was well reproduced by a computer simulation based on the phenomenological growth model where the slope angle dependence of lifetime of adatoms was taken into account. The lateral width of present nanowires could be kinetically controlled by the growth conditions and the supply thickness of AlGaN layers. (c) 2006 American Vacuum Society.
  • Taketomo Sato, Toshiyuki Fujino, Hideki Hasegawa
    APPLIED SURFACE SCIENCE 252 15 5457 - 5461 2006年05月 [査読有り][通常論文]
     
    Attempts were made to optimize the electrochemical anodization process for the formation of high-density, regular and straight nanopore arrays on InP. The structure, shape and size of the pores were very sensitive to substrate orientations, electrolyte concentrations and anodization voltages. Among (1 1 1)A, (1 1 1)B and (0 0 1) substrate orientations, the most uniform and most straight nanopore arrays were obtained on (0 0 1) substrates at anodization voltages of 5-7 V by using 1.0-1.5 M HCl electrolyte containing HNO3. The pore depth could be controlled up to 80 mu m by the anodization time. (c) 2005 Elsevier B.V. All rights reserved.
  • T Kimura, H Hasegawa, T Sato, T Hashizume
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 45 4B 3414 - 3422 2006年04月 [査読有り][通常論文]
     
    Hydrogen sensing characteristics of Pt/InP Schottky diodes fabricated by electro-deposition were investigated. Such diodes gave high Schottky barrier heights (SBHs) of 650-810 meV. Upon exposure to hydrogen in air, the diodes exhibited a remarkable increase in forward and reverse currents. The saturation current on a log scale and the transient speed changed in proportion to the square root of the hydrogen pressure, P-H2. Upon exposure to hydrogen in vacuum or in nitrogen, a much larger and much faster increase in current took place. However, the saturation Current was almost independent Of P-H2, and the current increase remained almost the same after the hydrogen was removed. The sensing mechanism is explained in terms of changes in SBH caused by interface dipoles formed at Pt/InP interfaces due to adsorbed atomic hydrogen. Transient waveforms and dependence of saturation current and transient time constant on P-H2 were explained quantitatively by a simple theory where processes including atomic hydrogen generation, transport; storage, adsorption, desorption, and reaction with oxygen are effectively included.
  • T Tamura, Tamai, I, S Kasai, T Sato, H Hasegawa, T Hashizume
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 45 4B 3614 - 3620 2006年04月 [査読有り][通常論文]
     
    The basic feasibility of constructing hexagonal binary decision diagram (BDD) quantum circuits on GaAs-based selectively grown (SG) nanowires was investigated front viewpoints of electrical connections through embedded nanowires and electrical-uniformity of devices formed on nanowires. For this, <(1) over bar 10 >- and < 510 >-oriented nanowires and hexagonal network structures combining these nanowires were formed on (001) GaAs substrates by selective molecular beam epitaxy (MBE) growth. The width and vertical position of the nanowires could be controlled by growth conditions for both <(1) over bar 10 >- and < 510 >-directions. By current-voltage (I-V) measurements, good electrical connection was confirmed at the node point where vertical alignment of embedded GaAs nanowire pieces was found to be important. SG quantum wire (QWR) switches formed on the nanowires showed good gate control over a wide temperature range with clear conductance quantization at low temperatures. Good device uniformities were obtained on the test chips, providing a good prospect for future integration. BDD node devices using SG QWR switches showed clear path switching characteristics. Estimated power-delay product values were very small, confirming the feasibility of ultra low-power operation of future circuits.
  • N Shiozaki, T Sato, M Akazawa, H Hasegawa
    JOURNAL DE PHYSIQUE IV 132 249 - 253 2006年03月 [査読有り][通常論文]
     
    For controlled low-damage etching of AlGaAs/GaAs nanostructures. fundamental properties of an etching process consisting of anodic oxidation and subsequent oxide dissolution are investigated both theoretically and experimentally. Anodic oxides formed on GaAs (001) and (111)B surfaces have the same composition and the same anodization parameters according to XPS, SEM and AFM measurements. The same applies to those formed on Al(0.3)Gi(0.7)As (001) and (111)B surfaces. The etching depth can be precisely controlled in nanometer scale by the anodization voltage. Selective etching was realized, using the lithography patterns. The surface morphology is much better than that in the standard wet chemical etching.
  • N Shiozaki, T Sato, M Akazawa, H Hasegawa
    JOURNAL DE PHYSIQUE IV 132 249 - 253 2006年03月 [査読有り][通常論文]
     
    For controlled low-damage etching of AlGaAs/GaAs nanostructures. fundamental properties of an etching process consisting of anodic oxidation and subsequent oxide dissolution are investigated both theoretically and experimentally. Anodic oxides formed on GaAs (001) and (111)B surfaces have the same composition and the same anodization parameters according to XPS, SEM and AFM measurements. The same applies to those formed on Al(0.3)Gi(0.7)As (001) and (111)B surfaces. The etching depth can be precisely controlled in nanometer scale by the anodization voltage. Selective etching was realized, using the lithography patterns. The surface morphology is much better than that in the standard wet chemical etching.
  • Toshiyuki Fujino, Takeshi Kimura, Taketomo Sato, Hideki Hasegawa, Tamotsu Hashizume
    e-Journal of Surface Science and Nanotechnology 4 184 - 191 2006年02月10日 [査読有り][通常論文]
     
    Attempts were made to form various nanostructures on InP substrates using anodization process. Surprisingly wide varieties of nanostructures were obtained. They included zigzag pore arrays and chaotic porous structures on (111)B substrate, and quasi-periodic straight nanopore arrays on (001) substrate. Straight pore samples showed blue-shifted peaks due to quantum confinement whereas no clear energy shifts were observed in (111)B samples. Zigzag and straight pore samples also showed red-shifted PL emissions probably due to emission from surface state continuum. © 2006 The Surface Science Society of Japan.
  • Isao Tamai, Taketomo Sato, Hideki Hasegawa, Tamotsu Hashizume
    e-Journal of Surface Science and Nanotechnology 4 19 - 24 2006年01月12日 [査読有り][通常論文]
     
    Attempts were made to further elaborate our experimental growth method and the theoretical growth simulation method for formation of AlGaAs/GaAs QWRs on the (111)B substrates, paying attention to Al composition dependence of growth. A series of repeated growth experiments were carried out on simple one-sided mesa patterns, and from their analysis of the results led to determination of parameter values needed for computer simulation based on the continuum model. The experimental evolution of the cross-sectional structures was well reproduced by simulation, not only on one-side mesa, but also on mesa stripes actually used for wire growth. Finally, an optimum growth design was derived for growth of an array of GaAs triangular QWRs with 40 nm base width on GaAs (111)B substrate by the simulation, and the actual growth experiment confirmed its realization. © 2006 The Surface Science Society of Japan.
  • Hideki Hasegawa, Taketomo Sato, Seiya Kasai, Boguslawa Adamowicz, Tamotsu Hashizume
    SOLAR ENERGY 80 6 629 - 644 2006年 [査読有り][招待有り]
     
    Characterization methods and fundamental aspects of surface/interface states and recombination process in Si and III-V materials are reviewed. Various measurement considerations are pointed out for the conventional metal-insulator-semiconductor (MIS) capacitance-voltage (C-P) method, a contactless C-V method, and the microscopic scanning tunneling spectroscopy (STS) method, and general features of surface states are discussed. Surface states are shown to have U-shaped distributions of donor acceptor continuum with a characteristic charge neutrality level, E-HO. Rigorous simulation of dynamics of surface recombination process has shown that the effective surface recombination velocity, S-eff, is not a constant of the surface, but its value changes by many orders of magnitude with the incident light intensity and the polarity and amount of fixed charge. From this, new methods of surface state characterization based on photoluminescence and cathodoluminescence are derived. Attempts to control surface states and Fermi level pinning at metal semiconductor interface and free surfaces of nano-structures are presented as efforts toward "nano-photovoltaics". (c) 2006 Elsevier Ltd. All rights reserved.
  • Takeshi Kimura, Hideki Hasegawa, Taketomo Sato, Tamotsu Hashizume
    2006 INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE AND RELATED MATERIALS CONFERENCE PROCEEDINGS 443 - + 2006年 [査読有り][通常論文]
     
    Hydrogen-sensing performances of Pt/InP Schottky diodes and MESFETs are evaluated from a viewpoint of constructing a nanometer-scale hydrogen sensor head of a future wireless hydrogen sensor chip. To realize large Schottky barrier heights (SBHs), Pt films were deposited by a pulsed in-situ electrochemical process. Upon exposure to hydrogen in air, the Pt/InP Schottky diode exhibited remarkably large increase of forward and reverse currents. The sensing mechanism is explained in terms of SBH changes caused by interface dipole formed at Pt/InP interface due to the adsorbed atomic hydrogen. Quantitative relationships between response magnitude and speed have been established. The Pt/InP MESFET also showed hydrogen induced current changes, and their magnitudes were much larger than those of the Schottky diode. Based on these, a novel structure of a nanometer-scale hexagonal hydrogen sensing head is proposed.
  • Hasegawa Hideki, Kasai Seiya, Sato Taketomo
    Frontiers in Electronics 41 421 - 436 2006年 [査読有り][通常論文]
  • 古川拓也, 木村健, 佐藤威友, 葛西誠也, 長谷川英機, 橋詰保
    電子情報通信学会技術研究報告. ED, 電子デバイス 105 326(ED2005 139-156) 39 - 42 2005年10月07日 [査読無し][通常論文]
  • 及川武, 佐藤威友, 長谷川英機, 橋詰保
    電子情報通信学会技術研究報告. ED, 電子デバイス 105 325(ED2005 118-138) 89 - 92 2005年10月06日 [査読無し][通常論文]
  • TAMAURA Takahiro, TAMAI Isao, KASAI Seiya, SATO Taketomo, HASEGAWA Hideki, HASHIZUME Tamotsu
    Extended abstracts of the ... Conference on Solid State Devices and Materials 2005 152 - 153 2005年09月13日 [査読無し][通常論文]
  • KIMURA Takeshi, HASEGAWA Hideki, SATO Taketomo, HASHIZUME Tamotsu
    Extended abstracts of the ... Conference on Solid State Devices and Materials 2005 218 - 219 2005年09月13日 [査読無し][通常論文]
  • T Sato, Tamai, I, H Hasegawa
    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 23 4 1706 - 1713 2005年07月 [査読有り][通常論文]
     
    The growth kinetics involved in the selective molecular beam epitaxy growth of GaAs quantum wires (QWRs) on mesa-patterned substrates is investigated in detail experimentally, and an attempt is made to model the growth theoretically, using a phenomenological continuum model. Experimentally, <-110 >-oriented QWRs were grown on (001) and (113)A substrates, and <-1-12 >-oriented QWRs were grown on (I I I)B substrates. From a detailed investigation of the growth profiles, it was found that the lateral wire width is determined by facet boundaries (FBs) within AlGaAs layers separating growth regions on top facets from those on side facets of mesa structures. Evolution of FBs during growth was complicated. For computer simulation, measured growth rates of various facets were fitted into a theoretical formula to determine the dependence of a lifetime of adatoms on the slope angle of the growing surface. The continuum model using the slope angle dependent lifetime reproduced the details of the experimentally observed growth profiles very well for growth on (001), (113)A, and (111)B substrates, including the complex evolution of facet boundaries (c) 2005 American Vacuum Society.
  • N Shiozaki, T Sato, H Hasegawa
    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 23 4 1714 - 1721 2005年07月 [査読有り][通常論文]
     
    Effects of surface states and surface passivation on photoluminescence (PL) properties of GaAs quantum wires (QWRs) are investigated. QWR samples were grown on (001) and (111)B substrates by the selective molecular beam epitaxy (MBE) method. For surface passivation, an ultrathin (about 1 nm) Si interface control layer (Si ICL) was grown by MBE as an interlayer. In both of the selectively grown QWRs on (001) and (111)B substrates, the PL intensity reduced exponentially with reduction of their wire-to-surface distance, being coexistent with a more gradual reduction due to carrier supply reduction. The exponential reduction was explained in terms of interaction between surface states and quantum confined states leading to tunneling assisted nonradiative recombination through surface states. Surface passivation by the Si-ICL method almost completely recovered PL intensities not only for QWRs on the (001) substrate, but also for QWRs on the (111)B substrate. (c) 2005 American Vacuum Society.
  • JIA Rui, KASAI Seiya, SATO Taketomo, HASEGAWA Hideki
    電子情報通信学会技術研究報告. ED, 電子デバイス 105 110 31 - 36 2005年06月03日 [査読無し][通常論文]
     
    Side-gating effects inhibiting the high-density integration of devices GaAs-based quantum wire transistors (QWRTrs) with nanosized Schottky gates controlling etched nanowires were investigated experimentally. Side-gating behaviors depended on the distance between the side-gate and nanowire edge d_<sg>, and when d_<sg><500nm and nanowire mesa etching was shallow, the large side-gating effect occurred, which could not be explained by the electrostatic effect. At the same time, anomalously large side-gate leakage current due to electron tunneling was observed. Here, we propose a model for the ...
  • 赤沢正道, 塩崎奈々子, 佐藤威友, 長谷川英機
    電子情報通信学会技術研究報告 105 110(ED2005 58-66) 25 - 30 2005年06月03日 [査読無し][通常論文]
  • T Oikawa, F Ishikawa, T Sato, T Hashizume, H Hasegawa
    APPLIED SURFACE SCIENCE 244 1-4 84 - 87 2005年05月 [査読有り][通常論文]
     
    This paper attempts to form AlGaN/GaN quantum wire (QWR) network structures on patterned GaN (0 0 0 1) substrates by selective molecular beam epitaxy (MBE) growth. Substrate patterns were prepared along < 1 1 2 0 > - and < 1 1 0 0 >-directions by electron cyclotron resonance assisted reactive-ion beam etching (ECR-RIBE) process. Selective growth was possible for both directions in the case of GaN growth, but only in the < 1 1 2 0 >-direction in the case of AlGaN growth. A hexagonal QWR network was successfully grown on a hexagonal mesa pattern by combining the < 1 1 2 0 >-direction and two other equivalent directions. AFM observation confirmed excellent surface morphology of the grown network. A clear cathodoluminescence (CL) peak coming from the embedded AlGaN/GaN QWR structure was clearly identified. (c) 2004 Published by Elsevier B.V.
  • H Hasegawa, T Sato
    ELECTROCHIMICA ACTA 50 15 3015 - 3027 2005年05月 [査読有り][招待有り]
     
    This paper reviews recent efforts by authors' group to utilize electrochemical processes for formation, processing and gate control of III-V semiconductor nanostructures. Topics include precise photo-anodic and pulsed anodic etching of InP, formation of arrays of < 001 >-oriented straight nanopores in n-type (001)InP by anodization and their possible applications and macroscopic and nanometer-scale metal contact formation on GaAs, InP and GaN by a pulsed in situ electrochemical process, which remarkably reduces Fermi level pinning. All the results indicate that electrochemical processes can achieve unique and important results, which the conventional semiconductor technology cannot realize, anticipating their increased importance in future semiconductor nanotechnology and nanoelectronics. (c) 2005 Elsevier Ltd. All rights reserved.
  • N Shiozaki, S Anantathanasarn, T Sato, T Hashizume, H Hasegawa
    APPLIED SURFACE SCIENCE 244 1-4 71 - 74 2005年05月 [査読有り][通常論文]
     
    Etched GaAs quantum wires (QWRs) and selectively grown (SG) QWRs were fabricated, and dependence of their photoluminescence (PL) properties on QWR width (W) and QWR distance to surface (d) were investigated. PL intensity greatly reduced with reduction of Wand d, due to non-radiative recombination through surface states. Surface passivation by growing a Si interface control layer (Si-ICL) on group III-terminated surfaces greatly improved PL properties. (c) 2004 Elsevier B.V. All rights reserved.
  • H Hasegawa, T Sato
    ELECTROCHIMICA ACTA 50 15 3015 - 3027 2005年05月 [査読有り][通常論文]
     
    This paper reviews recent efforts by authors' group to utilize electrochemical processes for formation, processing and gate control of III-V semiconductor nanostructures. Topics include precise photo-anodic and pulsed anodic etching of InP, formation of arrays of < 001 >-oriented straight nanopores in n-type (001)InP by anodization and their possible applications and macroscopic and nanometer-scale metal contact formation on GaAs, InP and GaN by a pulsed in situ electrochemical process, which remarkably reduces Fermi level pinning. All the results indicate that electrochemical processes can achieve unique and important results, which the conventional semiconductor technology cannot realize, anticipating their increased importance in future semiconductor nanotechnology and nanoelectronics. (c) 2005 Elsevier Ltd. All rights reserved.
  • T Sato, T Oikawa, H Hasegawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 44 4B 2487 - 2491 2005年04月 [査読有り][通常論文]
     
    The feasibility of the selective molecular beam epitaxy (MBE) growth of AlGaN/GaN quantum wire (QWR) Structures on prepatterned substrates is investigated. The detailed studies on growth features have revealed that size-reducing selective Growth is possible on mesa patterns having the (11-20)-orientation, but not on those having the (1-100)-orientations. The behavior reflects complex growth kinetics on high-index crystalline facets. The lateral wire width of QWR structures formed selectively on a top mesa can be controlled by adjusting the growth thickness and the initial size of mesa patterns. From cathodoluminescence (CL) measurements, emission from the embedded AlGaN/GaN QWR structure has been clearly identified.
  • Tamai, I, T Sato, H Hasegawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 44 4B 2652 - 2656 2005年04月 [査読有り][通常論文]
     
    The mechanism of the cross-sectional evolution during the selective growth of GaAs quantum wires (QWRs) on (111)B-patterned substrates was studied in detail both experimentally and theoretically. For this purpose, growth experiments were carried out on <-1-12 >-oriented wires by systematically changing growth conditions and pattern sizes. A detailed investigation on cross sections of wires has shown that the lateral wire width is determined by facet boundaries (FBs) within AlGaAs layers separating growth regions on top facets from those on side facets of mesa structures. FBs were found to be planar or curved, depending on initial pattern sizes and growth conditions. Computer simulation based on a phenomenological growth model was attempted, taking account of the facet-angle-dependent lifetime of adatoms. The simulation well reproduced the experimentally observed growth features including the evolution of FBs, indicating that the cross sections of wires grown on (111)B-patterned substrates are kinetically controlled by the pattern sizes and growth conditions.
  • 長谷川英機, 葛西誠也, 佐藤威友
    応用物理 74 3 320 - 326 2005年03月 [査読有り][招待有り]
  • 田村隆博, 湯元美樹, 玉井功, 葛西誠也, 佐藤威友, 長谷川英機
    電子情報通信学会技術研究報告 104 624(SDM2004 222-228) 19 - 24 2005年01月20日 [査読無し][通常論文]
  • RF-MBE選択成長法を用いたAlGaN/GaN細線ネットワークの形成
    及川 武, 佐藤威友, 長谷川英機, 橋詰 保
    電子情報通信学会技術研究報告,CPM CPM2005 134 89 - 92 2005年 [査読無し][通常論文]
  • T Kimura, T Sato, T Hashizume, H Hasegawa
    2005 International Conference on Indium Phosphide and Related Materials 533 - 536 2005年 [査読無し][通常論文]
     
    Pt Schottky diodes were fabricated on n-InP by pulsed electrodeposition, and their H-2 sensing properties were investigated. Deposition resulted in formation of Pt nanoparticles. As compared with diodes by vacuum deposition, electrodepositod diodes gave much higher Schottky barrier heights (SBHs) of 810 meV. They showed marked increase of the reverse current on exposure to H-2 gas in air. The magnitudes of current change and on-off transients depended on the partial pressure of H-2. The detection mechanism is explained in terms of SBH change caused by adsorption/desorption of atomic hydrogen at the Pt/semiconductor interface. Its behavior was strongly affected by the presence of oxygen in the atmosphere. Integration of the present sensor with a hexagonal quantum wire network is proposed for realization of a wireless hydrogen sensor chip.
  • ゲートレス型AlGaN/GaN -HEMTを利用した溶液センサ
    古川拓也, 木村健, 佐藤威友, 葛西誠也, 長谷川英機, 橋詰保
    電子情報通信学会技術研究報告,CPM CPM2005 134 39 - 42 2005年 [査読無し][通常論文]
  • H Hasegawa, S Kasai, T Sato
    IEICE TRANSACTIONS ON ELECTRONICS E87C 11 1757 - 1768 2004年11月 [査読有り][招待有り]
     
    A new approach for ultra-low-power LSIs based on quantum devices is presented and its present status and critical issues are discussed with a brief background review on the semiconductor nanotechnology. It is a hexagonal binary decision diagram (BDD) quantum logic circuit approach suitable for realization of ultra-low-power logic/mernory circuits to be used in new applications such as intelligent quantum (IQ) chips embedded in the ubiquitous network environment. The basic concept of the approach, circuit examples showing its feasibility, growth of high density nanostructure networks by molecular beam epitaxy (NIBE) for future LSI implementation, and the key processing issues including the device isolation issue are addressed.
  • SATO Taketomo, OIKAWA Takeshi, HASHIZUME Tamotsu, HASEGAWA Hideki
    Extended abstracts of the ... Conference on Solid State Devices and Materials 2004 814 - 815 2004年09月15日 [査読無し][通常論文]
  • TAMAI Isao, SATO Taketomo, HASEGAWA Hideki
    Extended abstracts of the ... Conference on Solid State Devices and Materials 2004 880 - 881 2004年09月15日 [査読無し][通常論文]
  • T Sato, Tamai, I, S Yoshida, H Hasegawa
    APPLIED SURFACE SCIENCE 234 1-4 11 - 15 2004年07月 [査読有り][通常論文]
     
    The mechanism determining heterointerface cross-sections is studied for GaAs ridge quantum wires (QWRs) grown by selective molecular beam epitaxy (MBE). Arrays of (-110)- and (-1-12)-orientated QWRs were grown on (001) and (111)B GaAs patterned substrates, respectively. A detailed investigation of cross-sections of wires has shown that the boundary planes appear on both sides of QWRs, keeping a constant angle, theta, with respect to the flat top of the substrate pattern, and they determine the lateral wire width. Their evolution mechanism has turned out to be a kinetic process, reflecting differences in migration and atom incorporation rates on different facets. Simple formulas for theta have been derived, and they have shown excellent agreements with experiment. This has led to precise kinetic control of the wire width by growth conditions. (C) 2004 Elsevier B.V. All rights reserved.
  • T Sato, Tamai, I, H Hasegawa
    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 22 4 2266 - 2274 2004年07月 [査読有り][通常論文]
     
    The growth kinetics involved in the selective molecular beam epitaxial growth of GaAs ridge QWRs is investigated in detail experimentally and an attempt is made to model the growth theoretically. For this purpose, detailed experiments were carried out on the growth of <110>-oriented AlGaAsGaAs ridge quantum wires on mesa-patterned (00 1) GaAs substrates. A phenomenological modeling was done based on the continuum approximation including parameters such as group III adatom lifetime, diffusion constant and migration length. Computer simulation using the resultant model well reproduces the experimentally observed growth features such as the cross-sectional structure of the ridge wire and its temporal evolution, its temperature dependence and evolution of facet boundary planes. The simple phenomenological model developed here seems to be very useful for design and precise control of the growth process. (C) 2004 American Vacuum Society.
  • S Yoshida, Tamai, I, T Sato, H Hasegawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 43 4B 2064 - 2068 2004年04月 [査読有り][通常論文]
     
    In view of applications to hexagonal binary decision diagram (BDD) quantum circuits, the growth of hexagonal GaAs nanowire networks was attempted by selective molecular beam epitaxy (MBE) on (111)B prepatterned substrates. The basic feasibility of <112>-oriented straight nanowires was first investigated. GaAs nanowires were selectively formed on the top (111)B plane of AlGaAs mesa structures with high uniformity. The lateral width of the wires was determined by two facet boundary planes separating the growth regions on the top and the side facets of the mesa structures. The angle of the boundary planes remained constant during growth, resulting in the wire width being precisely controlled by the thickness of the AlGaAs barrier layer. Then, GaAs/AlGaAs hexagonal nanowire networks were grown on the patterned substrates consisting of three equivalent <112>-oriented wires for a (111)B plane. The results of detailed structural and optical studies showed that highly uniform and smoothly connected hexagonal nanowire networks having threefold symmetry were successfully fabricated by the present selective MBE growth technique.
  • 石川史太郎, 及川武, 玉井功, 佐藤威友, 長谷川英機
    応用物理学関係連合講演会講演予稿集 51st 3 1540  2004年03月28日 [査読無し][通常論文]
  • Tamai, I, T Sato, H Hasegawa
    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 21 2-4 521 - 526 2004年03月 [査読有り][通常論文]
     
    Attempts were made to grow high-density GaAs hexagonal nano-wire networks on (001) patterned substrates by selective molecular beam epitaxy. To form a hexagon, (110)- and (510)-directions were combined. By the growth of straight wire arrays in each direction, the growth mode, conditions and mechanism were investigated. The wire width was shown to be determined for both directions by the facet boundary planes resulting from the growth rate difference on different facets. By optimizing growth conditions, highly uniform and smoothly connected hexagonal nano-wire networks with a density of 3 x 10(8) cm(-2) were successfully formed. (C) 2003 Elsevier B.V. All rights reserved.
  • Tamai, I, T Sato, H Hasegawa
    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 21 2-4 521 - 526 2004年03月 [査読有り][通常論文]
     
    Attempts were made to grow high-density GaAs hexagonal nano-wire networks on (001) patterned substrates by selective molecular beam epitaxy. To form a hexagon, (110)- and (510)-directions were combined. By the growth of straight wire arrays in each direction, the growth mode, conditions and mechanism were investigated. The wire width was shown to be determined for both directions by the facet boundary planes resulting from the growth rate difference on different facets. By optimizing growth conditions, highly uniform and smoothly connected hexagonal nano-wire networks with a density of 3 x 10(8) cm(-2) were successfully formed. (C) 2003 Elsevier B.V. All rights reserved.
  • 湯元美樹, 田村隆弘, 佐藤威友, 長谷川英機
    電子情報通信学会技術研究報告 103 631(SDM2003 213-221) 15 - 19 2004年01月30日 [査読無し][通常論文]
  • 吉田崇一, 玉井功, 佐藤威友, 長谷川英機
    電子情報通信学会技術研究報告 103 630(SDM2003 207-212) 23 - 28 2004年01月29日 [査読無し][通常論文]
  • M Yumoto, T Tamura, T Sato, H Hasegawa
    SUPERLATTICES AND MICROSTRUCTURES 34 3-6 485 - 491 2003年09月 [査読有り][通常論文]
     
    In view of applications to hexagonal binary decision diagram (BDD) LSIs, a first attempt is made to form quantum BDD node switches on selectively grown (SG) embedded quantum wires (QWRs) by molecular beam epitaxy (MBE). SG branch switches controlled by a Schottky wrap gate (WPG) were successfully fabricated by MBE growth and subsequent device processing. Gate control characteristics were studied by gate-dependent Shubnikov-de-Haas measurements, and the behavior was found to be similar to that of devices fabricated on wires by etching. The switch exhibited clear conductance quantization at low temperature, and temperature dependence of the voltage slope of conductance jump was clarified. A Y-branch BDD node device using two SG branch switches was successfully fabricated, and realized clear path switching characteristics. (C) 2004 Elsevier Ltd. All rights reserved.
  • 佐藤威友, 玉井功, 吉田崇一, 長谷川英機
    電子情報通信学会技術研究報告 103 117(ED2003 50-57) 29 - 34 2003年06月13日 [査読無し][通常論文]
  • 佐藤威友, 玉井功, 吉田崇一, 長谷川英機
    電子情報通信学会技術研究報告 102 640(SDM2002 244-251) 27 - 32 2003年02月10日 [査読無し][通常論文]
  • A Kameda, S Kasai, T Sato, H Hasegawa
    SOLID-STATE ELECTRONICS 47 2 323 - 331 2003年02月 [査読有り][通常論文]
     
    Effects of surface states on gate control characteristics of nano-meter scale Schottky gates formed on GaAs are investigated both theoretically and experimentally. Special sample structures are used. They are metal-insulator-semiconductor structures having nano-meter scale Schottky dot arrays for capacitance-voltage (C-V) measurements and metal-semi-conductor field effect transistor structures having nano-meter scale grating Schottky gates for current-voltage (I-V) measurements. Measured C-V and I-V results are compared with results of theoretical calculation on a computer. The effects of surface states are found to be two-fold. Namely, it is shown that control characteristics of nano-meter scale Schottky gates are strongly degraded by the presence of Fermi level pinning caused by surface states on the free surface surrounding the gate. It is also shown that a significant amount of gate-induced lateral charging of surface states takes place around the gate periphery, effectively increasing the gate dimension. These results indicate the critical importance of control of surface states in nano-devices using nano-meter scale Schottky gates. (C) 2002 Elsevier Science Ltd. All rights reserved.
  • T Sato, Tamai, I, H Hasegawa
    COMPOUND SEMICONDUCTORS 2002 174 3 145 - 148 2003年 [査読有り][通常論文]
     
    Selective MBE growth of an array of <-110>-oriented GaAs ridge QWRs was attempted on pre-patterned (001) substrates. Arrow-head shaped GaAs QWRs were selectively formed on the top (I 13)A facets of GaAs ridge structures. The underlying growth mechanism was clarified, and based on this, the wire width could be kinetically controlled by the growth process.
  • Seiya Kasai, Taketomo Sato, Hideki Hasegawa
    2003 International Semiconductor Device Research Symposium, ISDRS 2003 - Proceedings 482 - 483 2003年 [査読有り][通常論文]
     
    Explosive growth of intemets and wireless telephones starting in the late 20th century has opened up prospects towards an advanced ubiquitous network society. This also opens up new directions in the device research in addition to the continued efforts of scale down of Si CMOS device along the roadmap.
  • T Hirano, A Ito, T Sato, F Ishikawa, H Hasegawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 41 2B 977 - 981 2002年02月 [査読有り][通常論文]
     
    Attempts were made to optimize the parameters of the electrochemical process to form uniform nanopore arrays and utilize them as templates for molecular beam epitaxy (MBE) growth of InP-based quantum wires and quantum dots. Template parameters such as pore depth, diameter and period were strongly dependent on anodization conditions. In particular, in the pulsed anodization mode, the pore depth could be well controlled in the nanometer range by adjusting the number of the applied pulses. InGaAs MBE growth was attempted using the nanopore templates. Growth of InGaAs in pores occurred at a substantial depth of about 20-60 nm. The measured photoluminescence (PL) spectra had a new peak at about 1.2 eV in addition to the PL emission from the InP substrate and that from the InGaAs top layer. The new peak was tentatively assigned to the peak arising from InGaAs quantum wire arrays embedded in InP pores with a possible alloy composition change.
  • 玉井功, 佐藤威友, 長谷川英機
    電子情報通信学会技術研究報告 101 617(ED2001 224-231) 15 - 20 2002年01月28日 [査読無し][通常論文]
  • 平野哲郎, 佐藤威友, 長谷川英機
    電子情報通信学会技術研究報告 101 617(ED2001 224-231) 49 - 54 2002年01月28日 [査読無し][通常論文]
  • MBE選択成長法によるGaAs/AlGaAs量子細線の形成とその結合ネットワークへの応用
    玉井功, 佐藤威友, 長谷川英機
    電子情報通信学会研究会技術研究報告 ED2001 101/617 15 - 20 2002年 [査読無し][通常論文]
  • T Sato, Tamai, I, C Jiang, H Hasegawa
    COMPOUND SEMICONDUCTORS 2001 170 170 325 - 330 2002年 [査読有り][通常論文]
     
    Feasibility of formation of GaAs/AlGaAs hexagonal nanowire networks by selective MBE growth on patterned (001) substrates is investigated. First, the process for forming <(1) over bar 10>-oriented straight QWR arrays is studied and optimized with respect to wire shape, size and uniformity. SEM and PL studies showed that arrow-head shaped GaAs nanowires can be formed on the top of (113) AlGaAs ridge with excellent size controllability and high uniformity. Feasibility study of hexagonal nanowire network formation by combining different pattern orientations has shown combination of <(1) over bar 10>- and <510>- directions is most promising.
  • Selective MBE Growth of <-110>- and <510>- Oriented GaAs Ridge Quantum Wires on Patterned (001) Substrates for Formation of Hexagonal Nanowire Networks
    Sato Taketomo, Tamai Isao, Jiang Chao, Hasegawa Hideki
    The Second International Workshop on Quantum Nonplanar Nanostructures & Nanoelectronics 283 - 286 2002年 [査読無し][通常論文]
  • 電気化学的手法によるInPポーラス構造の形成と応用
    平野 哲郎, 佐藤 威友, 長谷川 英機
    電子情報通信学会研究会技術研究報告 ED2001 101-617/ 49 - 54 2002年 [査読無し][通常論文]
  • 平野哲郎, 佐藤威友, 伊藤章, 石川史太郎, 長谷川英機
    応用物理学会学術講演会講演予稿集 62nd 3 1059  2001年09月11日 [査読無し][通常論文]
  • T Sato, S Kasai, H Hasegawa
    APPLIED SURFACE SCIENCE 175 181 - 186 2001年05月 [査読有り][通常論文]
     
    The electrical properties of nanometer-sized Schottky contacts which were successfully formed on n-GaAs and n-InP substrates by a combination of an electrochemical process and an electron-beam (EB) lithography. were characterized both experimentally and theoretically. The detailed I-ri measurements using a conductive AFM system showed nonlinear log I-ii characteristics with large n value in range of 1.2-2.0 which cannot be explained by a standard 1D thermionic emission model. A computer simulation showed that this nonlinear characteristics can be explained by a new 3D thermionic emission model where Fermi-level pinning on the surrounding free surface modifies the potential distribution underneath the nano-contact. Calculation of C-V characteristics showed an extremely small change of the depletion layer width with bias due to the environmental Fermi-level pinning. On the other hand, it was also found that Fermi-level pinning at the metal-semiconductor interface itself is greatly reduced, resulting in a strong dependence of barrier height on the metal workfunction. (C) 2001 Elsevier Science B.V. All rights reserved.
  • 平野哲郎, 佐藤威友, 伊藤章, 石川史太郎, 長谷川英機
    応用物理学関係連合講演会講演予稿集 48th 3 1378  2001年03月28日 [査読無し][通常論文]
  • T Sato, S Kasai, H Hasegawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 40 3B 2021 - 2025 2001年03月 [査読有り][通常論文]
     
    The electrical properties of nanometer-sized Schottky contacts formed on n-GaAs and n-InP substrates by an in situ electrochemical process were studied both experimentally and theoretically to understand and improve their gate control behavior in single electron devices and quantum devices. From the current-voltage (I-V) measurements using a conductive atomic force microscope (AFM) system, the nano-Schottky contacts showed nonlinear log I-V characteristics with large and voltage-dependent n values which cannot be explained by the 1D thermionic emission model. The behavior was explained by a novel 3D thermionic emission model including 3D potential distribution modified by an environmental Fermi-level pinning. The depletion characteristics were calculated on the basis of the new model including the environmental effects. The results showed small changes of the depletion layer width with a bias underneath the nano-Schottky contacts due to the environmental Fermi-level pinning. Control of Fermi-level pinning is thus crucial to obtain nano devices in the quantum regime that exhibit good behavior.
  • T Sato, S Kasai, H Hasegawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 40 3B 2021 - 2025 2001年03月 [査読有り][通常論文]
     
    The electrical properties of nanometer-sized Schottky contacts formed on n-GaAs and n-InP substrates by an in situ electrochemical process were studied both experimentally and theoretically to understand and improve their gate control behavior in single electron devices and quantum devices. From the current-voltage (I-V) measurements using a conductive atomic force microscope (AFM) system, the nano-Schottky contacts showed nonlinear log I-V characteristics with large and voltage-dependent n values which cannot be explained by the 1D thermionic emission model. The behavior was explained by a novel 3D thermionic emission model including 3D potential distribution modified by an environmental Fermi-level pinning. The depletion characteristics were calculated on the basis of the new model including the environmental effects. The results showed small changes of the depletion layer width with a bias underneath the nano-Schottky contacts due to the environmental Fermi-level pinning. Control of Fermi-level pinning is thus crucial to obtain nano devices in the quantum regime that exhibit good behavior.
  • A Kameda, S Kasai, T Sato, H Hasegawa
    2001 INTERNATIONAL SEMICONDUCTOR DEVICE RESEARCH SYMPOSIUM, PROCEEDINGS 626 - 629 2001年 [査読無し][通常論文]
  • T Hirano, A Ito, T Sato, F Ishikawa, H Hasegawa
    2001 INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE AND RELATED MATERIALS, CONFERENCE PROCEEDINGS 378 - 381 2001年 [査読無し][通常論文]
     
    In this study, attempts were made to optimize the parameters of the electrochemical process to form uniform nanopore arrays in order to utilize them as templates for MBE growth of InP-based quantum wires and quantum dots. Template parameters such as the pore depth, diameter and period were strongly dependent on anodization conditions. Especially, in the pulsed anodization mode, the pore depth could be well controlled in the nanometer range by changing the number of the applied pulses. InGaAs MBE growth was attempted using the nanopore templates. Growth of InGaAs in pores took place into a substantial depth of about 100-200 nm. The measured PL spectrum had a new peak at about 1.2 eV in addition to the PL emission from the InP substrate and that of InGaAs top layer. The new peak was tentatively assigned to be from InGaAs quantum wire arrays embedded in InP pores with a possible alloy composition change.
  • H Hasegawa, T Sato, S Kasai
    APPLIED SURFACE SCIENCE 166 1-4 92 - 96 2000年10月 [査読有り][通常論文]
     
    Transport properties of two types of electrochemically produced nanometer-sized GaAs and InP Schottky contacts were investigated. One is macroscopic contacts containing many nano-dots and the other is isolated single-dot contacts. Macroscopic contacts showed near ideal thermionic emission characteristics with ideality factors close to unity. I-V characteristics of single nano-dor, contacts directly measured by a conductive AFM probe showed nonlinear log I-V behavior with large and voltage-dependent ideality factors. The latter was explained by potential profile modification due to Fermi level pinning on surrounding free surfaces. Both types of contacts indicated that Fermi level pinning disappears as the dot size is reduced, indicating that strong Fermi level pinning is not intrinsic to Schottky contacts. (C) 2000 Elsevier Science B.V. All rights reserved.
  • T Sato, S Kasai, H Okada, H Hasegawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 39 7B 4609 - 4615 2000年07月 [査読有り][通常論文]
     
    The current transport characteristics of nanometer-sized Schottky contacts were investigated from theoretical and experimental viewpoints. A theoretical calculation of the three dimensional (3D) potential distributions showed that the potential shape underneath the nano-Schottky contacts was considerably modified by the surface Fermi level pinning on the air exposed free surfaces, producing a saddle point in the potential. The curl ent-voltage (I-V) curves were strongly influenced by this saddle point potential and resulted in nonlinear log I-V characteristics. Experimentally, the Pt nano-particles were selectively formed using the in situ electrochemical process on n-type GaAs and n-type InP substrates patterned using electron-beam (EB) lithography. Their I-V measurements were carried out using an atomic force microscopy (AFM) system equipped with a conductive probe. The log I-V curves of the nano-Schottky contacts showed nonlinear characteristics with large n values of 1.96 for n-GaAs and 1.27 for n-InP and could be very well explained by the theoretical I-V curves considering the "environmental" Fermi level pinning.
  • H Fujikura, AM Liu, A Hamamatsu, T Sato, H Hasegawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 39 7B 4616 - 4620 2000年07月 [査読有り][通常論文]
     
    Recently, (001)-oriented nanometer-sized pores (nano-pores) without side branches, unlike porous Si, have been realized by our group on (001) n-InP surfaces by means of electrochemical anodization in 1M HCl solution. However, they exhibit large structural nonuniformity including the presence of an irregular top layer, random pore positioning and wavy pore walls. In this study, attempts have been made to improve pore uniformity and to clarify their optical properties. Anodization in 1M HCl + HNO3 solution realized highly uniform nano-pore arrays consisting of square-shaped straight pores defined by four crystalline (011) facets. This improvement is explained in terms of preferential etching along the vertical (001)-direction at the pore tip due to the slow etching rate along the lateral (011)-direction as well as the uniform supply of reactant species to pore tips realized by the removal of the irregular top layer during the anodization process. The nano-pore arrays show strong blue- and red-shifted photoluminescence emissions at high and low temperatures, respectively. These are assigned as emissions due to the transition between electron and hole quantum states inside the pore walls and that involving a broad surface state continuum at pore wall surfaces, respectively.
  • 佐藤威友, 葛西誠也, 岡田浩, 長谷川英機
    電子情報通信学会技術研究報告 99 616(ED99 306-318) 79 - 84 2000年02月10日 [査読無し][通常論文]
  • H Fujikura, AM Liu, T Sato, T Hirano, H Hasegawa
    2000 INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE AND RELATED MATERIALS, CONFERENCE PROCEEDINGS 510 - 513 2000年 [査読有り][通常論文]
     
    High density, uniform arrays of (001)-oriented straight nanopores were successfully formed on (001) n-InP surfaces in a self-assembled fashion by electrochemical anodization in 1M HCl + HNO3 solution. Unlike porous Si, the pores do not have side branches and possessed nearly equal-sized square-shapes defined by four crystalline flat (110) facets. Preferential etching along vertical (001)-direction due to slow etching rates on (110) side facets may be responsible for formation of such a uniform structure. At low temperature, the nanopore arrays showed strong red-shifted photoluminescence (PL) emission probably due to a transition involving a broad surface state continuum at the pore wall surfaces. On the other hand, a strong blue-shifted PL emission was observed at room temperature, confirming presence of quantum size effect in the pore walls as expected from the structural observations.
  • H Hasegawa, T Sato, C Kaneshiro
    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 17 4 1856 - 1866 1999年07月 [査読有り][通常論文]
     
    The properties of GaAs and InP Schottky diodes having nanometer-sized metal dots were investigated in order to clarify whether or not strong Fermi level pinning is an intrinsic property of the metal-semiconductor interface. Macroscopic Schottky diode samples having many nanometer-sized metal dots as well as single-dot Schottky diode samples were prepared by an in situ electrochemical process which consisted of pulsed anodic etching of the semiconductors followed by subsequent de or pulsed cathodic deposition of the metal. Strong Fermi level pinning was not seen in the GaAs and InP macroscopic samples. The Schottky barrier height SBH values were strongly dependent on the metal work function and on the electrochemical processing conditions. Of particular interest, the difference in the dot size changed the SBH almost 340 meV in Pt/InP macroscopic Schottky diodes, indicating that Fermi level pinning disappears as the dot size is sufficiently reduced. X-ray photoelectron spectroscopy and Raman measurements indicated that these interfaces are oxide and stress free. Use of an atomic force microscope with a conductive probe allowed direct I-V measurements on single-dot samples. The metal work function and dot size dependencies of the SBHs in these samples were similar to those in macroscopic samples. Large ideality factors observed in the single-dot sample were explained in terms of environmental Fermi level pinning which produces a saddle point potential. The metal work function dependence of the SBHs measured as well as the relationship between the SBH and the ideality factor were both far from what was found in recent predictions based on the metal-induced gap state model. All the experimental results were consistently explained by the disorder-induced gap state model which asserts that strong Fermi level pinning is an extrinsic property of the metal-semiconductor interface. (C) 1999 American Vacuum Society. [S0734-211X(99)04704-6].
  • 佐藤威友, 岡田浩, 長谷川英機
    電子情報通信学会技術研究報告 99 21(ED99 1-10) 39 - 44 1999年04月22日 [査読無し][通常論文]
  • T Sato, C Kaneshiro, H Okada, H Hasegawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 38 4B 2448 - 2452 1999年04月 [査読有り][通常論文]
     
    Attempts were made to form regular arrays of size- and position-controlled Pt-dots on GaAs and InP by combining an ir? situ electrochemical process with the electron beam (EB) lithography. This utilizes the precipitation of Pt nano-particles at the initial stage of electrodeposition. First, electrochemical conditions were optimized in the mode of self-assembled dot array formation on unpatterned substrates. Minimum in-plane dot diameters of 22 nm and 26 nm on GaAs and InP. respectively, were obtained under the optimal pulsed mode. Then, Pt dots were selectively formed on patterned substrates with open circular windows formed by EB lithography, thereby realizing dot-position control. The Pt dot was round to have been deposited at the center of each open window, and the in-plane diameter of the dot could be controlled by the number, width and period of the pulse-waveform applied to substrates. A minimum diameter of 20 nm was realized in windows with a diameter of 100 nm, using a single pulse. Current-voltage (I-V) measurements using an atomic force microscopy (AFM) system with a conductive probe indicated that each Pt dot/n-GaAs contact possessed a high Schottky barrier height of about 1 eV.
  • T Sato, C Kaneshiro, H Hasegawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 38 2B 1103 - 1106 1999年02月 [査読有り][通常論文]
     
    In order to investigate the correlation between the microstructure of a metal/semiconductor (M/S) interface and the Schottky barrier height (SBH), Pt Schottky contacts were formed on n-type InP by an in situ electrochemical process under various electrochemical conditions; they were then investigated using scanning electron microscopy (SEM), current-voltage (I-V) and capacitance-voltage (C-V) measurements. Electrodeposition resulted in the formation of arrays of nanometer-sized Pt particles whose distribution strongly depended on electrochemical conditions. The SBH values exhibited a strong correlation with the particle distribution, leading to a high SBH value of 0.86 eV under the condition of the most uniform distribution of the smallest particles. The result is discussed from the viewpoint of the disorder-induced gap state (DIGS) model.
  • C Kaneshiro, T Sato, H Hasegawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 38 2B 1147 - 1152 1999年02月 [査読有り][通常論文]
     
    Using voltammetry, X-ray photoemission spectroscopy (XPS), in situ electrochemical scanning tunneling microscopy (STM), ex situ atomic force microscopy (AFM) and scanning electron microscope (SEM) measurements, electrochemical etching modes for n-InP surfaces were investigated and optimized for uniform and controlled etching in an HCl electrolyte. The voltammograms indicated the presence of active and passive regions. The surfaces obtained in the active region were clean and featureless with an rms roughness of 1.8 nm. On the other hand, the oxide cove:red surfaces obtained in the passive region were nonuniform and porous. Etching characteristics of the d.c. photo-anodic mode and the pulsed avalanche mode were then investigated and compared. Both modes were found to be highly controllable and produced uniform and clean surfaces, consuming eight holes per molecule of InP. In particular, the pulsed avalanche etching mode realized an extremely high etch depth controllability of 3 x 10(-5) nm/pulse.
  • C Kaneshiro, T Sato, H Hasegawa
    COMPOUND SEMICONDUCTORS 1998 162 585 - 590 1999年 [査読有り][通常論文]
     
    K Ni, Co and Sn Schottky barriers were formed on n-GaAs by an in situ electrochemical process which consists of anodic etching and subsequent metal deposition in the same electrolyte. All the fabricated diodes showed nearly ideal thermionic emission transport. The Schottky barrier heights were found to be strongly dependent on the metal work function, giving a large value of slope factor of S=0.18-0.55. The result was far away from the recent prediction based on MIGS model. Based on SEM/AFK XPS and Raman measurements, the result was explained by the DIGS model.
  • Hiroshi Okada, Taketomo Sato, Kei-ichiroh Jinushi, Hideki Hasegawa
    Microelectronic Engineering 47 1-4 285 - 287 1999年 [査読無し][通常論文]
  • 兼城千波, 佐藤威友, 小山雄司, 橋詰保, 長谷川英機
    電子情報通信学会技術研究報告 98 185(ED98 84-97) 55 - 60 1998年07月22日 [査読無し][通常論文]
  • 佐藤威友, 兼城千波, 岡田浩, 長谷川英機
    電子情報通信学会技術研究報告 98 184(ED98 76-83) 21 - 26 1998年07月21日 [査読無し][通常論文]
  • T Sato, C Kaneshiro, H Hasegawa
    1998 INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE AND RELATED MATERIALS - CONFERENCE PROCEEDINGS 623 - 626 1998年 [査読有り][通常論文]
     
    InP and related materials are attractive materials for high speed electronic and optoelectronic devices. Technologically, well-controllable metal/semiconductor (M/S) interface with high Schottky barrier heights (SBHs) in nano-scale are required for the realizability and the high reliability of nano-scaled electronic devices. However, metal/n-InP contacts generally produces low SBH values of typically about 450meV. SBH values can not be increased by using contact metals with large workfunctions due to so-called Fermi-level pinning. In contrast to this, we have recently shown that the SBH value of the Pt/n-InP contacts can be increased up to 860meV[1] by using an in situ pulsed electrochemical process. This process has also been shown to be useful for the Schottky gate formation for MESFETs and HEMTs[2,3]. The purpose of this paper is to optimize the electrochemical process for high SBHs by investigating the correlation between the microstructures of metal/n-InP interfaces having nano-scale metal particles and the SBHs.
  • C Kaneshiro, T Sato, H Hasegawa
    1998 INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE AND RELATED MATERIALS - CONFERENCE PROCEEDINGS 191 - 194 1998年 [査読有り][通常論文]
     
    Electrochemical etching of n-InP surfaces is studied by using voltammetry, XPS, in situ electrochemical STM, ex situ AFM and SEM measurements in order to characterize and optimize the etching process. The voltammograms indicated occurrence of the active-passive transition. The surfaces etched by the optimal anodic condition were clean and featureless with an rms roughness of 2.5 nm, whereas the surfaces obtained in the passive region were porous. The optimum avalanche pulse etching mode realized an extremely high etch depth controllability of 6 x 10(-5) nm/pulse.
  • H Hasegawa, T Sato, H Okada, K Jinushi, S Kasai, Y Satoh
    APPLIED SURFACE SCIENCE 123 335 - 338 1998年01月 [査読有り][通常論文]
     
    In order to realize high temperature operating quantum devices, this paper attempts to form nm-size Schottky in-plane gate (IPG) and wrap gate (WPG) structures on GaAs- and InP-based nanostructures by an in-situ electrochemical process. Pulsed electrodeposition of Pt was found to be optimal, realizing nearly pinning-free high Schottky barrier heights as well as fine and highly uniform nm-size grains with minimal stress. Using the optimized process, quantum wire transistors and single electron transistors were successfully realized on GaAs etched 2DEG bars and on MBE grown InGaAs ridge quantum wires. (C) 1998 Elsevier Science B.V.
  • 佐藤威友, 橋詰保, 長谷川英機
    電子情報通信学会技術研究報告 97 158(ED97 65-74) 13 - 18 1997年07月14日 [査読無し][通常論文]
  • H Hasegawa, T Sato, T Hashizume
    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 15 4 1227 - 1235 1997年07月 [査読有り][通常論文]
     
    Recently, unusually high Schottky barrier heights (SBHs) have been realized by our group on n-type InP and related materials by an in situ electrochemical deposition of Pt. In an attempt to understand the underlying mechanism of the SBH enhancement, this article investigates in detail the evolution process of the metal (Pt, Ni, Co, and Ag)-InP interface during the in situ electrochemical process, using current-voltage, capacitance voltage, deep level transient spectroscopy, x-ray photoelectron spectroscopy, Raman, atomic force microscope, and scanning electron microscope measurements. Pt deposition by the electrochemical process realized an oxide-free, defect-free, stress-free, and nearly pinning-free interface, whereas Pt deposition by conventional electron beam evaporation and sputtering processes as well as Ag, Ni, and Co deposition by the electrochemical process gave rise to stressed and pinned interfaces. The observed large process dependence of SBH can be explained by none of the metal induced gap state model, the unified defect model, and the effective workfunction model. It is explained here by the disorder induced gap state model. (C) 1997 American Vacuum Society.
  • T Sato, S Uno, T Hashizume, H Hasegawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 36 3B 1811 - 1817 1997年03月 [査読有り][通常論文]
     
    Pt Schottky barriers were formed on InP-based materials by a novel in-situ, electrochemical process. electrical characteristics, surfaces and interfaces of the Schottky diodes were investigated by current-voltage (IV), capacitance-voltage (C-V), deep-level transient spectroscopy (DLTS) and atomic force microscopy (AFM) measurements. The mechanism for increasing the Schottky barrier heights (SBH) was explained in terms of possible ordered interface formation from the viewpoint of the disorder induced gap state (DIGS) model.
  • T Sato, H Hasegawa
    1997 INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE AND RELATED MATERIALS - CONFERENCE PROCEEDINGS 517 - 520 1997年 [査読有り][通常論文]
     
    Recently the so-called InP-based materials such as InP, In0.52Al0.48As and In0.53Ga0.47As have become important materials for high speed electronic and optoelectronic devices. A common drawback of these materials is, however, that Schottky barrier heights (SBHs) on n-type materials are generally low. Typical SBH values are 0.45eV, 0.60eV and 0.20eV for n-InP, In0.52Al0.48As and In0.53Ga0.47As, respectively. Technologically low SBH values are problematic and impose severe limitations on the realizability of MESFETs and MSM photoditectors, and performance and reliability of HEMTs. In an attempt to overcome this difficulty, we have recently found that the SBH value of the Pt/n-InP Schottky diode can be increased up to 0.86 eV by using a novel in-situ electrochemical process,[1] and have succeeded in realization of well-behaved InP MESFETs[2] for the first time. The purpose of the present paper is further to understand and optimize the electrochemical process in view of its possible application to formation of fine Schottky gate electrodes for InP-based HEMTs utilizing InAlAs/InGaA s/InAlAs/InP heterostructures. First, electrodeposition conditions and metal selection were optimized for InP for higher SBHs. Then, applicability of the electrochemical process for formation of Schottky gate was confirmed directly on HEMT wafers. Finally, the possible mechanism for the observed SBH increase is briefly discussed.
  • 佐藤威友, 橋詰保, 長谷川英機
    電子情報通信学会技術研究報告 96 352(ED96 112-119) 9 - 15 1996年11月08日 [査読無し][通常論文]
  • SATO Taketomo, UNO Shouichi, HASHIZUME Tamotsu, HASEGAWA Hideki
    Extended abstracts of the ... Conference on Solid State Devices and Materials 1996 106 - 108 1996年08月26日 [査読無し][通常論文]
  • S Uno, T Hashizume, T Sato, H Hasegawa
    1996 EIGHTH INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE AND RELATED MATERIALS 338 - 341 1996年 [査読有り][通常論文]

書籍

  • Lateral Alignment of Epitaxial Quantum Dots
    HASEGAWA Hideki, SATO Taketomo, KASAI Seiya (担当:分担執筆範囲:24 Large-Scale Integration of Quantum Dot Devices on MBE-Based Quantum Wire Networks)
    Springer 2007年

講演・口頭発表等

  • 光電気化学エッチング法を用いたAlGaInN/AlGaNリセスゲートHFETの作製  [通常講演]
    伊藤滉朔, 小松裕斗, 渡久地政周, 井上暁喜, 三好実人, 佐藤威友
    第68回応用物理学会春季学術講演会 口頭発表(一般)
  • コンタクトレス光電気化学エッチングによるリセスゲートAlGaN/GaN HEMT の作製  [通常講演]
    渡久地政周, 三輪和希, 堀切文正, 福原昇, 成田好伸, 吉田丈洋, 佐藤威友
    第68回応用物理学会春季学術講演会 口頭発表(一般)
  • Precise control in threshold voltage of AlGaN/GaN HEMTs utilizing a photoelectrochemical (PEC) etching  [通常講演]
    T. Sato, M. Toguchi, K. Itoh, T. Hashizume
    The 8th Asian Conference on Crystal Growth and Crystal Technology (CGCT-8)
  • Recessed-gate AlGaN/GaN HEMTs fabricated by photo-electrochemical (PEC) etching  [通常講演]
    T. Sato, T. Hashizume
    Virtual Workshop on Materials Science and Advanced Electronics Created by Singularity 口頭発表(一般)
  • n+GaN基板上n-GaN層の光電気化学(PEC)エッチング時のカソード電極
    福原昇, 堀切文正, 渡久地政周, 三輪和希, 大神洸貴, 佐藤威友
    応用物理学会春季学術講演会講演予稿集(CD-ROM) 2021年
  • 半導体ナノ構造を利用した高感度化学センサの開発(依頼講演)  [招待講演]
    佐藤威友
    第6回北海道大学部局横断シンポジウム 2020年10月 シンポジウム・ワークショップパネル(公募)
  • Fabrication of Recessed-Gate AlGaN/GaN HEMTs Utilizing Contactless Photo-Electrochemical (CLPEC) Etching  [通常講演]
    M. Toguchi, K. Miwa, F. Horikiri, N. Fukuhara, Y. Narita, O. Ichikawa, R. Isono, T. Tanaka, T. Sato
    2020 Pacific Rim Meeting on Electrochemical and Solid State Science (PRiME 2020) 口頭発表(一般)
  • Photo-Electrochemical Etching and Porosification of III-Nitride Semiconductors (Invited)  [招待講演]
    T. Sato, M. Toguchi
    2020 Pacific Rim Meeting on Electrochemical and Solid State Science (PRiME 2020) 口頭発表(招待・特別)
  • GaN Wet Etching Process for HEMT Devices (invited)  [招待講演]
    F. Horikiri, N. Fukuhara, M. Toguchi, T. Sato
    International symposium on Advanced Plasma Science and its Applications for Nitrides and Nanomaterials 口頭発表(招待・特別)
  • 電気化学的手法を用いたICP-RIE加工n-GaN表面の評価
    武田健太郎, 山田真嗣, 山田真嗣, 渡久地政周, 加地徹, 佐藤威友
    応用物理学会春季学術講演会講演予稿集(CD-ROM) 2020年
  • GaNの光電気化学(PEC)エッチングが有する可能性 3)加熱によるエッチング速度の向上
    堀切文正, 福原昇, 太田博, 浅井直美, 成田好伸, 吉田丈洋, 三島友義, 渡久地政周, 三輪和希, 大神洸貴, 佐藤威友
    応用物理学会春季学術講演会講演予稿集(CD-ROM) 2020年
  • 加熱による硫酸ラジカルの生成とn-GaN光電気化学(PEC)エッチングへの応用
    三輪和希, 大神洸貴, 渡久地政周, 堀切文正, 福原昇, 成田好伸, 吉田丈洋, 佐藤威友
    応用物理学会春季学術講演会講演予稿集(CD-ROM) 2020年
  • 電気めっき法によるGaNへのPt電極の形成と電気特性評価
    小原康, 島内道人, 佐藤威友, 本久順一
    応用物理学会北海道支部/日本光学会北海道支部合同学術講演会講演予稿集 2020年
  • コンタクトレス光電気化学(PEC)エッチングを用いたリセスゲートHEMTの作製
    堀切文正, 福原昇, 渡久地政周, 三輪和希, 成田好伸, 市川磨, 磯野僚多, 田中丈士, 佐藤威友
    電子情報通信学会技術研究報告 2020年
  • Simple Photoelectrochemical Etching of GaN for RF Application  [通常講演]
    F. Horikiri, N. Fukuhara, Y. Narita, T. Yoshida, M. Toguchi, K. Miwa, T. Sato
    Materials Research Meeting 2019
  • Contactless Photoelectrochemical Etching of n-GaN in K2S2O8 solution  [通常講演]
    M. Toguchi, K. Miwa, F. Horikiri, N. Fukuhara, Y. Narita, T. Yoshida, T. Sato
    Materials Research Meeting 2019 ポスター発表
  • Precise Control in Threshold Voltage of AlGaN/GaN HEMTs by Photoelectrochemical Etching  [通常講演]
    Y. Komatsu, M. Toguchi, T. Sato
    Materials Research Meeting 2019 ポスター発表
  • Fabrication of GaN nanowires by wet processes using electrodeless photo-assisted electro- chemical etching and alkaline solution treatment  [通常講演]
    M. Shimauchi, K. Miwa, M. Toguchi, T. Sato, J. Motohisa
    The 9th Asia-Pacific Workshop on Widegap Semiconductors ポスター発表
  • Evaluation of Radical Production Rate from S2O82- ions for GaN Etching  [通常講演]
    M. Toguchi, K. Miwa, F. Horikiri, N. Fukuhara, Y. Narita, T. Yoshida, T. Sato
    The 9th Asia-Pacific Workshop on Widegap Semiconductors ポスター発表
  • Simple Photoelectrochemical Etching for GaN HEMT Application  [通常講演]
    F. Horikiri, N. Fukuhara, Y. Narita, T. Yoshida, M. Toguchi, K. Miwa, T. Sato
    The 9th Asia-Pacific Workshop on Widegap SemiconductorsThe 9th Asia-Pacific Workshop on Widegap Semiconductors ポスター発表
  • Precise control in recessed-gate etching for AlGaN/GaN HEMTs by utilizing photo- electrochemical reactions  [通常講演]
    Y. Komatsu, M. Toguchi, T. Sato
    The 9th Asia-Pacific Workshop on Widegap Semiconductors ポスター発表
  • III-V族化合物半導体のウェットエッチング 〜窒化物半導体に関する最近の話題を中心に〜  [招待講演]
    佐藤 威友, 渡久地 政周
    2019 第80回 応用物理学会 秋季学術講演会 2019年09月 口頭発表(招待・特別)
  • コンタクトレス光電気化学エッチング及びウェットエッチングによる窒化ガリウムナノワイヤの作製  [通常講演]
    島内 道人, 三輪 和希, 渡久地 政周, 佐藤 威友, 本久 順一
    2019 第80回 応用物理学会 秋季学術講演会 2019年09月 口頭発表(一般)
  • 高濃度n型GaN基板に対する光電気化学(PEC)エッチングの調査  [通常講演]
    三輪 和希, 渡久地 政周, 佐藤 威友
    2019 第80回 応用物理学会 秋季学術講演会 2019年09月 ポスター発表
  • AlGaInN/AlGaNヘテロ構造の光電気化学エッチング(2)  [通常講演]
    小松 祐斗, 渡久地政周, 斉藤 早紀, 三好 実人, 佐藤 威友
    2019 第80回 応用物理学会 秋季学術講演会 2019年09月 ポスター発表
  • K2S2O8/H3PO4混合溶液を用いたn-GaNのコンタクトレスエッチング  [通常講演]
    渡久地 政周, 三輪 和希, 堀切 文正, 福原 昇, 成田 好伸, 吉田 丈洋, 佐藤 威友
    2019 第80回 応用物理学会 秋季学術講演会 2019年09月 口頭発表(一般)
  • 電気化学インピーダンス法を用いたn-GaN加工表面の評価 (2)  [通常講演]
    武田 健太郎, 渡久地 政周, 佐藤 威友
    2019 第80回 応用物理学会 秋季学術講演会 2019年09月 ポスター発表
  • GaN Wet Etching Process for Power and RF Devices  [招待講演]
    F. Horikiri, N. Fukuhara, H. Ohta, N. Asai, Y. Narita, T. Yoshida, T. Mishima, M. Toguchi, K. Miwa, T. Sato
    2019 International Conference on Solid State Devices and Materials 2019年09月 口頭発表(招待・特別)
  • Characterization of processing-damage induced on n-GaN surface utilizing electrochemical methods  [通常講演]
    Kentaro Takeda, Masachika Toguchi, Taketomo Sato
    13th Topical Workshop on Heterostructure Microelectronics 2019年08月 ポスター発表
  • Photo-electrochemical etching optimized for high-doped n-type GaN  [通常講演]
    Kazuki Miwa, Masachika Toguchi, Taketomo Sato
    13th Topical Workshop on Heterostructure Microelectronics 2019年08月 ポスター発表
  • GaN Wet Etching Process  [招待講演]
    Fumimasa Horikiri, Noboru Fukuhara, Hiroshi Ohta, Naomi Asai, Yoshinobu Narita, Takehiro Yoshida, Tomoyoshi Mishima, Masachika Toguchi, Kazuki Miwa, Taketomo Sato
    13th Topical Workshop on Heterostructure Microelectronics 2019年08月 口頭発表(招待・特別)
  • 窒化物半導体の電気化学エッチングとデバイス応用(招待講演)  [招待講演]
    日本表面真空学会 関西支部 合同セミナー2019 2019年07月 口頭発表(招待・特別)
  • GaN Wet Etching Process for Power and RF Devices  [招待講演]
    Fumimasa Horikiri, Noboru Fukuhara, Hiroshi Ohta, Naomi Asai, Yoshinobu Narita, Takehiro Yoshida, Tomoyoshi Mishima, Masachika Toguchi, Kazuki Miwa, Taketomo Sato
    2019 Asia-Pacific Workshop on Fundamentals and Applications of Advanced Semiconductor Devices 2019年07月 口頭発表(招待・特別)
  • Damage-less Wet Etching for Normally-off AlGaN/GaN HEMTs using Photo-electrochemical Reactions  [招待講演]
    Taketomo Sato, Keisuke Uemura, Masachika Toguchi
    2019 International Conference on Compound Semiconductor Manufacturing Technology 2019年05月 口頭発表(招待・特別) Minneapolis, USA
  • Electrochemical characterization of etching damage induced to n-GaN surface  [通常講演]
    K. Takeda, M. Toguchi, T. Sato
    11th International Symposium on Advanced Plasma Science and its Applications for Nitride and Nanomaterials 2019年03月 口頭発表(一般)
  • Low-damage wet etching for AlGaN/GaN recessed-gate HEMTs using photo-electrochemical reactions  [通常講演]
    K. Uemura, Y. Komatsu, T. Sato
    11th International Symposium on Advanced Plasma Science and its Applications for Nitride and Nanomaterials 2019年03月 口頭発表(一般)
  • 光電気化学エッチングによる窒化ガリウムの微細加工の検討  [通常講演]
    島内道人, 三輪和希, 渡久地政周, 佐藤威友, 本久順一
    第66回応用物理学会春季学術講演会 2019年03月 口頭発表(一般)
  • AlGaInN/AlGaNヘテロ構造の光電気化学エッチング  [通常講演]
    小松祐斗, 植村圭佑, 佐藤威友
    第66回応用物理学会春季学術講演会 2019年03月 口頭発表(一般)
  • ペルオキソ二硫酸イオン(S2O82-)含有電解液におけるGaNの電気化学特性  [通常講演]
    渡久地政周, 三輪和希, 堀切文正, 福原昇, 成田好伸, 吉田丈洋, 佐藤威友
    第66回応用物理学会春季学術講演会 2019年03月 口頭発表(一般)
  • GaNの光電気化学(PEC)エッチングが有する可能性②コンタクトレスでのエッチング  [通常講演]
    堀切文正, 福原昇, 太田博, 浅井直美, 成田好伸, 吉田丈洋, 三島友義, 渡久地政周, 三輪和希, 佐藤威友
    第66回応用物理学会春季学術講演会 2019年03月 口頭発表(一般) 東京工業大学大岡山キャンパス,東京都目黒区
  • Effect of Photo-electrochemical Etching and Post-metallization Annealing on Gate-controllability of AlGaN/GaN High Electron Mobility Transistors  [通常講演]
    K. Uemura, M. Deki, Y. Honda, H. Amano, T. Sato
    International Workshop on Nitride Semiconductors 2018 (IWN2018) 2018年11月 口頭発表(一般)
  • Low-damage Etching for GaN-based Electronic Devices utilizing Photo-electrochemical Reactions  [招待講演]
    佐藤 威友
    4th Intensive Discussion on Growht of Nitride Semiconductors 2018年11月 口頭発表(招待・特別)
  • Fabrication of GaN Porous Nanostructures utilizing Electrochemical Reactions  [通常講演]
    T. Sato
    HU-SNU Joint Symposium 2018年11月 口頭発表(一般)
  • Precise thickness control in recess-etching for normally-off AlGaN/GaN HEMTs using a photo-electrochemical reaction  [通常講演]
    K. Uemura, Y. Komatsu, T. Sato
    HU-SNU Joint Symposium 2018年11月 ポスター発表
  • Electrochemical Formation and Application of Porous Gallium Nitride  [招待講演]
    T. Sato, M. Toguchi
    Americas International Meeting on Electrochemistry and Solid State Science (AiMES 2018) 2018年10月 口頭発表(招待・特別)
  • 小松祐斗, 植村圭佑, 渡久地政周, 佐藤威友
    電気化学秋季大会講演要旨集(CD‐ROM) 2018年09月
  • 渡久地政周, 武田健太郎, 佐藤威友
    電気化学秋季大会講演要旨集(CD‐ROM) 2018年09月
  • 武田健太郎, 渡久地政周, 佐藤威友
    応用物理学会秋季学術講演会講演予稿集(CD-ROM) 2018年09月
  • Recessed-gate AlGaN/GaN High Electron Mobility Transistors (HEMTs) Prepared by Photo-electrochemical Etching and Post-metallization Annealing  [通常講演]
    K. Uemura, M. Deki, Y. Honda, H. Amano, T. Sato
    第79 回応用物理学会秋季大会、19p-CE-4(日韓ジョイントシンポジウム 2018年09月 口頭発表(一般)
  • Control of Pore Depth in GaN Porous Structures Utilizing a Photoabsorption Process Under below-Bandgap Illumination  [通常講演]
    M. Toguchi, S. Matsumoto, T. Sato
    233rd ECS Meeting 2018年05月 ポスター発表
  • Precisely-controlled etching of gallium nitride utilizing electrochemical reactions  [招待講演]
    T. Sato, M. Toguchi
    Nanotech Malaysia 2018 2018年05月 口頭発表(招待・特別)
  • 渡久地政周, 佐藤威友
    電気化学会大会講演要旨集(CD-ROM) 2018年02月
  • 光電気化学反応を利用した窒化物半導体の低損傷エッチングと電子デバイスへの応用  [通常講演]
    植村圭佑, 松本悟, 渡久地政周, 伊藤圭亮, 佐藤 威友
    電子情報通信学会 電子デバイス研究会 2017年12月 口頭発表(一般)
  • Improved wet-etching processes for GaN-based electron devices  [招待講演]
    T. Sato, K. Uemura, T. Hashizume
    2017 MRS Fall Meeting and Exhibit 2017年11月 口頭発表(招待・特別)
  • Photo-electrochemical Formation of Porous Nanostructures on n-type GaN utilizing Franz-Keldysh Effect  [通常講演]
    M. Toguchi, S. Matsumoto, T. Sato
    The 8th International Symposium on Surface Science (ISSS8) 2017年10月 ポスター発表
  • Removal of reactive-ion-etching damage from n-GaN surface using a photoelectrochemical process  [通常講演]
    S. Matsumoto, M. Toguchi, T. Sato
    2017 International Conference on Solid State Devices and Materials (SSDM 2017) 2017年09月 口頭発表(一般)
  • 渡久地政周, 佐藤威友
    電気化学秋季大会講演要旨集(CD‐ROM) 2017年08月
  • 松本悟, 佐藤威友, 成田哲生, 成田哲生, 加地徹, 橋詰保, 橋詰保
    応用物理学会秋季学術講演会講演予稿集(CD-ROM) 2017年08月
  • 植村圭佑, 佐藤威友, 橋詰保
    応用物理学会秋季学術講演会講演予稿集(CD-ROM) 2017年08月
  • Highly-controllable etching for AlGaN/GaN recessed-gate structures utilizing low-damage electrochemical reactions  [通常講演]
    K. Uemura, Y. Kumazaki, T. Sato, T. Hashizume
    12th Topical Workshop on Heterostructure Microelectronics (TWHM 2017) 2017年08月 ポスター発表
  • Precise thickness control in recess-etching for normally-off AlGaN/GaN HEMTs using a low damage photo-electrochemical reaction  [通常講演]
    T. Sato, K. Uemura, Y. Kumazaki, T. Hashizume
    12th International Conference on Nitride Semiconductors (ICNS 12) 2017年07月 ポスター発表
  • 佐藤威友, 熊崎祐介, 松本悟
    電気化学会大会講演要旨集(CD-ROM) 2017年03月
  • 伊藤圭亮, ZHANG Xiaoyi, 熊崎祐介, 佐藤威友
    応用物理学会春季学術講演会講演予稿集(CD-ROM) 2017年03月
  • 枝元将彰, 松本悟, 熊崎祐介, 佐藤威友
    応用物理学会春季学術講演会講演予稿集(CD-ROM) 2017年03月
  • 近江沙也夏, 熊崎祐介, 佐藤威友
    応用物理学会春季学術講演会講演予稿集(CD-ROM) 2017年03月
  • 松本悟, 熊崎祐介, 佐藤威友
    応用物理学会北海道支部・日本光学会北海道地区合同学術講演会講演予稿集 2017年01月
  • 植村圭佑, 熊崎祐介, 佐藤威友
    応用物理学会北海道支部・日本光学会北海道地区合同学術講演会講演予稿集 2017年01月
  • 伊藤圭亮, ZHANG Xiaoyi, 熊崎祐介, 佐藤威友
    応用物理学会北海道支部・日本光学会北海道地区合同学術講演会講演予稿集 2017年01月
  • Electrochemical formation of N-type GaN and N-type InP porous structures for chemical sensor applications  [通常講演]
    T. Sato, X. Zhang, K. Ito, S. Matsumoto, Y. Kumazaki
    IEEE SENSORS 2016 2016年11月 ポスター発表
  • Precise Structural Tuning of Porous GaN Using Two-Step Anisotropic Etching for Optical and Photo-Electric Applications  [通常講演]
    Y. Kumazaki, S. Matsumoto, T. Sato
    2016 Pacific Rim Meeting on Electrochemistry and Solid State Science (PRiME 2016) 2016年10月 口頭発表(一般)
  • Electrochemical Formation and Characterization of Cu2O Films on n-type InP Porous Structures  [通常講演]
    S. Omi, Y. Kumazaki, T. Sato
    2016 Pacific Rim Meeting on Electrochemistry and Solid State Science (PRiME 2016) 2016年10月 ポスター発表
  • 松本悟, 熊崎祐介, 佐藤威友
    応用物理学会秋季学術講演会講演予稿集(CD-ROM) 2016年09月
  • 近江沙也夏, 熊崎祐介, 佐藤威友
    応用物理学会秋季学術講演会講演予稿集(CD-ROM) 2016年09月
  • 喜田弘文, 伊藤圭亮, 熊崎祐介, 渡久地政周, 佐藤威友
    応用物理学会秋季学術講演会講演予稿集(CD-ROM) 2016年09月
  • 伊藤圭亮, ZHANG Xiaoyi, 喜田弘文, 熊崎祐介, 佐藤威友
    応用物理学会秋季学術講演会講演予稿集(CD-ROM) 2016年09月
  • 熊崎祐介, 植村圭佑, 佐藤威友
    応用物理学会秋季学術講演会講演予稿集(CD-ROM) 2016年09月
  • 近江沙也夏, 熊崎祐介, 佐藤威友
    応用物理学会春季学術講演会講演予稿集(CD-ROM) 2016年03月
  • 熊崎祐介, 松本悟, 佐藤威友
    応用物理学会春季学術講演会講演予稿集(CD-ROM) 2016年03月
  • 喜田弘文, 伊藤圭亮, 熊崎祐介, 佐藤威友
    応用物理学会春季学術講演会講演予稿集(CD-ROM) 2016年03月
  • 枝元将彰, 熊崎祐介, 佐藤威友
    応用物理学会春季学術講演会講演予稿集(CD-ROM) 2016年03月
  • Interface control technologies for high-power GaN transistors: Self-stopping etching of p-GaN layers utilizing electrochemical reactions  [招待講演]
    T. Sato, Y. Kumazaki, M. Edamoto, M. Akazawa, T. Hashizume
    SPIE Photonics West 2016 2016年02月 口頭発表(招待・特別)
  • Photoelectric energy conversion in GaN porous nanostructures formed by electrochemical process  [招待講演]
    T. Sato, Y. Kumazaki, T. Hashizume
    Energy, Materials and Nanotechnology 2015年12月 口頭発表(招待・特別)
  • Size-controlled formation of high-aspect ratio porous nanostructures on GaN substrates utilizing photo-assisted electrochemical etching for photovoltaic applications  [通常講演]
    Y. Kumazaki, Z. Yatabe, T. Sato
    2015 MRS Fall Meeting & Exhibit 2015年11月 ポスター発表
  • Effect of High Electric Field on Photoabsorption Properties of GaN Porous Structures  [通常講演]
    T. Sato, Y. Kumazaki, Z. Yatabe
    228th ECS meeting, Hyatt Regency Phoenix and Phoenix Convention Center 2015年10月 口頭発表(一般)
  • Formation of Self-aligned Pore Arrays on n-GaN Substrates by Photo-assisted Electrochemical Etching Process  [通常講演]
    Y. Kumazaki, T. Sato, Z. Yatabe
    2015 International Conference on Solid State Devices and Materials (SSDM 2015) 2015年09月 口頭発表(一般)
  • 枝元将彰, 熊崎祐介, 谷田部然治, 佐藤威友
    応用物理学会秋季学術講演会講演予稿集(CD-ROM) 2015年08月
  • 近江沙也夏, 熊崎祐介, 谷田部然治, 佐藤威友
    応用物理学会秋季学術講演会講演予稿集(CD-ROM) 2015年08月
  • 熊崎祐介, 近江沙也夏, 谷田部然治, 佐藤威友
    応用物理学会秋季学術講演会講演予稿集(CD-ROM) 2015年08月
  • 喜田弘文, 熊崎祐介, 谷田部然治, 佐藤威友
    応用物理学会秋季学術講演会講演予稿集(CD-ROM) 2015年08月
  • High-selective etching of p-GaN layers on AlGaN/GaN heterostructures by electrochemical process  [通常講演]
    M. Edamoto, Y. Kumazaki, Z. Yatabe, T. Sato, T. Hashizume
    11th Topical Workshop on Heterostructure Microelectronics (TWHM 2015) 2015年08月 ポスター発表
  • Electrochemical Formation of Cu2O Films on n-type InP and n-type GaN Substrates  [通常講演]
    S. Omi, Y. Kumazaki, Z. Yatabe, T. Sato
    11th Topical Workshop on Heterostructure Microelectronics (TWHM 2015) 2015年08月 ポスター発表
  • Photoelectrochemical characterization of n-type GaN porous structures for use in photocatalytic water-splitting system  [通常講演]
    H. Kida, Y. Kumazaki, Z. Yatabe, T. Sato
    11th Topical Workshop on Heterostructure Microelectronics (TWHM 2015) 2015年08月 ポスター発表
  • Influence of dry etching on Al2O3/AlGaN/GaN MOS interface properties  [通常講演]
    Z. Yatabe, J. Ohira, T. Sato, T. Hashizume
    11th Topical Workshop on Heterostructure Microelectronics (TWHM 2015) 2015年08月 ポスター発表
  • Electrochemical formation of GaN porous structures for photocatalytic applications  [招待講演]
    T. Sato, Y. Kumazaki, Z. Yatabe
    11th Topical Workshop on Heterostructure Microelectronics (TWHM 2015) 2015年08月 口頭発表(招待・特別)
  • 喜田弘文, 熊崎祐介, 谷田部然治, 佐藤威友
    電子情報通信学会技術研究報告 2015年07月
  • 熊崎祐介, 渡部晃生, 谷田部然治, 佐藤威友
    電子情報通信学会技術研究報告 2015年05月
  • 谷田部然治, 大平城二, 佐藤威友, 橋詰保
    応用物理学会春季学術講演会講演予稿集(CD-ROM) 2015年02月
  • 熊崎祐介, 近江沙也夏, 谷田部然治, 佐藤威友
    応用物理学会春季学術講演会講演予稿集(CD-ROM) 2015年02月
  • 渡部晃生, 熊崎祐介, 谷田部然冶, 佐藤威友
    応用物理学会北海道支部・日本光学会北海道地区合同学術講演会講演予稿集 2015年01月
  • 宮本貴雄, 小西敬太, 佐藤威友
    応用物理学会北海道支部・日本光学会北海道地区合同学術講演会講演予稿集 2015年01月
  • Correlation between growth time and carrier density in epitaxial graphene on 6H-SiC  [通常講演]
    T. Miyamoto, K. Konishi, T. Sato
    The 7th International Symposium on Surface Science (ISSS2014) 2014年11月 ポスター発表
  • Structural Properties and Control of GaN Porous Nanostructures Formed by Photo-assisted Electrochemical Process  [通常講演]
    A. Watanabe, Y. Kumazaki, Z. Yatabe, T. Sato
    The 7th International Symposium on Surface Science (ISSS2014) 2014年11月 ポスター発表
  • Enhanced spin-orbit interaction in the hydrogenated epitaxial graphene on silicon carbide  [通常講演]
    K. Konishi, T. Miyamoto, K. Yoh, T. Sato
    27th International Microprocesses and Nanotechnology Conference (MNC2014) 2014年11月 ポスター発表
  • Electrochemical Formation of GaN Porous Structures Under UV-Light Irradiation for Photoelectrochemical Application  [通常講演]
    T. Sato, A. Watanabe, Y. Kumazaki, Z. Yatabe
    2014 ECS and SMEQ Joint International Meeting 2014年10月 口頭発表(一般)
  • 渡部晃生, 熊崎祐介, 谷田部然治, 佐藤威友
    電気化学秋季大会講演要旨集 2014年09月
  • 佐藤威友, 熊崎祐介, 渡部晃生, 谷田部然治
    応用物理学会秋季学術講演会講演予稿集(CD-ROM) 2014年09月
  • 宮本貴雄, 小西敬太, 佐藤威友
    応用物理学会秋季学術講演会講演予稿集(CD-ROM) 2014年09月
  • 熊崎祐介, 渡部晃生, 谷田部然治, 佐藤威友
    応用物理学会秋季学術講演会講演予稿集(CD-ROM) 2014年09月
  • Correlation between Structural and Optical Properties of GaN Porous Structures Formed by Photo-assisted Electrochemical Etching  [通常講演]
    Y. Kumazaki, A. Watanabe, Z. Yatabe, T. Sato
    The International Workshop on Nitride Semiconductors 2014 (IWN2014) 2014年08月
  • Interface Trap States in Al2O3/AlGaN/GaN Structure Induced by ICP Etching of AlGaN Surfaces  [招待講演]
    Z. Yatabe, T. Sato, T. Hashizume
    The International Workshop on Nitride Semiconductors 2014 (IWN2014) 2014年08月
  • Structural control of GaN porous structures for high-sensitive chemical sensors  [通常講演]
    A. Watanabe, Y. Kumazaki, Z. Yatabe, T. Sato
    The 6th IEEE International Nanoelectronics Conference 2014 (INEC-2014) 2014年07月
  • Electrochemical Formation of III-V Semiconductor Porous Nanostructures  [招待講演]
    T. Sato, Y. Kumazaki, A. Watanabe, Z. Yatabe
    The 6th IEEE International Nanoelectronics Conference 2014 (INEC-2014) 2014年07月
  • 佐藤 威友, 渡部 晃生, 熊崎 祐介
    公益社団法人電気化学会第81回大会 2014年03月 口頭発表(一般)
  • 佐藤威友, 渡部晃生, 熊崎祐介
    Chem Sens 2014年03月
  • 橋詰 保, 谷田部 然治, 佐藤 威友
    電気学会電子デバイス研究会 2014年03月 口頭発表(招待・特別)
  • 佐藤威友, 赤澤正道, 橋詰保
    応用物理学会春季学術講演会講演予稿集(CD-ROM) 2014年03月 口頭発表(招待・特別)
  • 熊崎祐介, 佐藤威友, 橋詰保, 橋詰保
    応用物理学会春季学術講演会講演予稿集(CD-ROM) 2014年03月 口頭発表(一般)
  • 渡部晃生, 熊崎祐介, 谷田部然冶, 佐藤威友
    応用物理学会北海道支部・日本光学会北海道地区合同学術講演会講演予稿集 2013年12月 口頭発表(一般)
  • Photoabsorption and Photoelectric Conversion Properties of InP Porous Structures Formed by Electrochemical Process  [通常講演]
    SATO Taketomo, KUMAZAKI Yusuke, JINBO Ryohei, YATABE Zenji
    224th Meeting of the Electrochemical Society(CD-ROM) 2013年10月 口頭発表(一般)
  • Structural and Optical Characterization of GaN Porous Structures Formed by Photo-assisted Electrochemical Process  [通常講演]
    KUMAZAKI Yusuke, WATANABE Akio, YATABE Zenji, SATO Taketomo
    224th Meeting of the Electrochemical Society(CD-ROM) 2013年10月 ポスター発表
  • 渡部晃生, 熊崎祐介, 谷田部然治, 佐藤威友
    応用物理学会秋季学術講演会講演予稿集(CD-ROM) 2013年08月
  • 熊崎祐介, 渡部晃生, 谷田部然治, 佐藤威友
    応用物理学会秋季学術講演会講演予稿集(CD-ROM) 2013年08月
  • Selective etching of p-GaN layers for normally-off AlGaN/GaN HEMTs by electrochemical process  [通常講演]
    KUMAZAKI Yusuke, AZUMAISHI Naoki, UEDA Hiroyuki, KANECHIKA Masakazu, TOMITA Hidemoto, SATO Taketomo, HASHIZUME Tamotsu
    10th International Conference on Nitride Semiconductors (ICNS-10) 2013年08月 ポスター発表
  • Electrochemical Formation and Optical Characterization of GaN Porous Structures  [通常講演]
    KUMAZAKI Yusuke, WATANABE Akio, JINBO Ryohei, YATABE Zenji, SATO Taketomo
    32nd Electronic Materials Symposium (EMS32) 2013年07月
  • 電気化学的手法による半導体多孔質構造の形成と機能素子への応用  [招待講演]
    佐藤 威友
    第 29 回ライックセミナー・第 19 回若手研究者交流会 2013年06月 公開講演,セミナー,チュートリアル,講習,講義等
  • 電気化学的手法によるGaN多孔質構造の形成と光学特性の評価  [通常講演]
    熊崎 祐介, 渡部 晃生, 谷田部 然治, 佐藤 威友
    第 29 回ライックセミナー・第 19 回若手研究者交流会 2013年06月 公開講演,セミナー,チュートリアル,講習,講義等
  • 熊崎祐介, 神保亮平, 谷田部然治, 佐藤威友
    電子情報通信学会技術研究報告 2013年05月
  • Electrochemical Formation and Optical Characterization of GaN Porous Structures  [通常講演]
    KUMAZAKI Yusuke, WATANABE Akio, JINBO Ryohei, YATABE Zenji, SATO Taketomo
    The 40th International Symposium on Compound Semiconductors (ISCS2013) 2013年05月 ポスター発表
  • 熊崎祐介, 渡部晃生, 神保亮平, 谷田部然治, 佐藤威友
    応用物理学会春季学術講演会講演予稿集(CD-ROM) 2013年03月
  • 神保亮平, 渡部晃生, 佐藤威友
    応用物理学会北海道支部・日本光学会北海道地区合同学術講演会講演予稿集 2013年01月
  • High-sensitive ISFETs Based on Semiconductor Porous Nanostructures  [招待講演]
    SATO Taketomo
    BIT’s 3rd Annual World Congress of NanoMedicine-2012 2012年11月 口頭発表(一般)
  • Photoelectric-conversion Devices Based on InP Porous Structure  [通常講演]
    SATO Taketomo, JINBO Ryohei, YATABE Zenji
    2012 Pacific Rim Meeting on Electrochemical and Solid-State Science 2012年10月 口頭発表(一般)
  • Optical Absorption Properties of InP Porous Structures Formed by Electrochemical Process  [通常講演]
    KUMAZAKI Yusuke, KUDO, Tomohito, YATABE Zenji, SATO Taketomo
    2012 International Conference on Solid State Devices and Materials 2012年09月 ポスター発表
  • 熊崎祐介, 工藤智人, 谷田部然冶, 佐藤威友
    応用物理学会学術講演会講演予稿集(CD-ROM) 2012年08月
  • 神保亮平, 今井雄大, 谷田部然治, 佐藤威友
    応用物理学会学術講演会講演予稿集(CD-ROM) 2012年08月
  • 神保亮平, 谷田部然冶, 佐藤威友
    応用物理学関係連合講演会講演予稿集(CD-ROM) 2012年02月
  • Photo-electrical response of InP porous structures formed on pn substrates  [通常講演]
    KUDO Tomohito, SATO Taketomo
    Extended Abstracts of the 2011 International Symposium on Surface Science 2011年12月
  • Photoelectric Conversion Devices based on InP Porous Structures  [通常講演]
    JINBO Ryohei, KUDO Tomohito, SATO Taketomo
    Extended Abstracts of the 2011 International Conference on Solid State Devices and Materials 2011年09月
  • 神保亮平, 岡崎拓行, 佐藤威友
    応用物理学会学術講演会講演予稿集(CD-ROM) 2011年08月
  • 工藤智人, 佐藤威友
    応用物理学会学術講演会講演予稿集(CD-ROM) 2011年08月
  • 今井雄大, 神保亮平, 谷田部然治, 佐藤威友
    応用物理学会学術講演会講演予稿集(CD-ROM) 2011年08月
  • 谷田部然冶, 東石直樹, 佐藤威友, 橋詰保
    応用物理学会学術講演会講演予稿集(CD-ROM) 2011年08月
  • 今井雄大, 岡崎拓行, 佐藤威友
    応用物理学関係連合講演会講演予稿集(CD-ROM) 2011年03月
  • 工藤智人, 岡崎拓行, 佐藤威友
    応用物理学関係連合講演会講演予稿集(CD-ROM) 2011年03月
  • 岡崎拓行, 神保亮平, 佐藤威友
    化学系学協会北海道支部冬季研究発表会講演要旨集 2011年02月
  • 今井雄大, 岡崎拓行, 佐藤威友
    応用物理学会北海道支部・日本光学会北海道地区合同学術講演会講演予稿集 2011年01月
  • 工藤智人, 岡崎拓行, 佐藤威友
    応用物理学会北海道支部・日本光学会北海道地区合同学術講演会講演予稿集 2011年01月
  • High-Sensitive ISFETs based on InP Porous Structures  [通常講演]
    SATO Taketomo, YOSHIZAWA Naoki
    The 61st Annual Meeting of the International Society of Electrochemistry(CD-ROM) 2010年09月
  • 岡崎拓行, 佐藤威友
    応用物理学会学術講演会講演予稿集(CD-ROM) 2010年08月
  • 今井雄大, 岡崎拓行, 佐藤威友
    応用物理学会学術講演会講演予稿集(CD-ROM) 2010年08月
  • 佐藤威友, 岡崎拓行
    応用物理学会学術講演会講演予稿集(CD-ROM) 2010年08月
  • 佐藤威友, 岡崎拓行
    応用物理学会学術講演会講演予稿集(CD-ROM) 2010年08月
  • 工藤智人, 岡崎拓行, 佐藤威友
    応用物理学会学術講演会講演予稿集(CD-ROM) 2010年08月
  • Optical and Electrical Properties of InP Porous Structures Formed on P-N Substrates  [通常講演]
    OKAZAKI Hiroyuki, SATO Taketomo, YOSHIZAWA Naoki, HASHIZUME Tamotsu
    2010 International Conference on Indium Phosiphide and Related Materials 2010年05月
  • 岡崎拓行, 吉澤直樹, 佐藤威友, 橋詰保
    応用物理学関係連合講演会講演予稿集(CD-ROM) 2010年03月
  • Optical and electrical properties of InP porous structures formed on p-n substrates  [通常講演]
    OKAZAKI Hiroyuki, YOSHIZAWA Naoki, SATO Taketomo, HASHIZUME Tamotsu
    2010 International RCIQE/CREST Joint Workshop 2010年03月
  • 岡崎拓行, 吉澤直樹, 佐藤威友
    応用物理学会北海道支部・日本光学会北海道地区合同学術講演会講演予稿集 2010年01月
  • 吉澤直樹, 岡崎拓行, 佐藤威友, 橋詰保
    応用物理学会北海道支部・日本光学会北海道地区合同学術講演会講演予稿集 2010年01月
  • Low Reflectance Surface Observed on InP Porous Structures after Photoelectrochemical Etching  [通常講演]
    SATO Taketomo, YOSHIZAWA Naoki, OKAZAKI Hiroyuki, HASHIZUME Tamotsu
    216th Meeting of the Electrochemical Society(CD-ROM) 2009年10月
  • 岡崎拓行, 吉澤直樹, 佐藤威友
    応用物理学会学術講演会講演予稿集 2009年09月
  • 吉澤直樹, 岡崎拓行, 佐藤威友, 橋詰保
    応用物理学会学術講演会講演予稿集 2009年09月
  • Formation and application of InP porous structures on p-n substrates  [通常講演]
    SATO Taketomo, YOSHIZAWA Naoki, OKAZAKI Hiroyuki, HASHIZUME Tamotsu
    2009 Asia-Pacific Workshop on Fundamentals and Applications of Advanced Semiconductor Devices(CD-ROM) 2009年06月
  • pH Response Characteristics of Liquid-phase Chemical Sensors using InP Open-gate FETs  [通常講演]
    YOSHIZAWA Naoki, SATO Taketomo, MIZOHATA Akinori, HASHIZUME Tamotsu
    2009 RCIQE International Seminar on "Advanced Semiconductor Materials and Devices" 2009年03月
  • Electrochemical formation and sensor application of InP porous nanostructures  [通常講演]
    SATO Taketomo, MIZOHATA Akinori, YOSHIZAWA Naoki, HASHIZUME Tamotsu
    2009 RCIQE International Seminar on "Advanced Semiconductor Materials and Devices" 2009年03月
  • pH Sensitivity of Liquid-phase Chemical Sensors using InP Open-gate FETs  [通常講演]
    YOSHIZAWA Naoki, SATO Taketomo, MIZOHATA Akinori, HASHIZUME Tamotsu
    2008 International Symposium on Surface Science and Nanotechnology 2008年11月
  • Liquid-phase Chemical Sensors using InP-based Open-gate FETs  [通常講演]
    YOSHIZAWA Naoki, SATO Taketomo, MIZOHATA Akinori
    The Seventh IEEE Conference on Sensors 2008年10月
  • Complete Removal of Irregular Top Layer for Sensor Applications of InP Porous Nanostructures  [通常講演]
    SATO Taketomo, MIZOHATA Akinori, YOSHIZAWA Naoki, HASHIZUME Tamotsu
    2008 Pacific Rim Meeting on Electrochemicao and Solid-State Science (CD-ROM) 2008年10月
  • 吉澤直樹, 溝畑彰規, 佐藤威友, 橋詰保
    応用物理学会学術講演会講演予稿集 2008年09月
  • 塩崎奈々子, 佐藤威友, 橋詰保
    応用物理学会学術講演会講演予稿集 2008年09月
  • 溝畑彰規, 吉澤直樹, 佐藤威友, 橋詰保
    応用物理学会学術講演会講演予稿集 2008年09月
  • 佐藤威友, 溝畑彰規, 吉澤直樹, 橋詰保
    応用物理学会学術講演会講演予稿集 2008年09月
  • Electrochemical formation and functionalization of InP porous nanostructures and their application to chemical sensors  [通常講演]
    MIZOHATA Akinori, YOSHIZAWA Naoki, SATO Taketomo, HASHIZUME Tamotsu
    2008 Asia-Pacific Workshop on Fundamentals and Applications of Advanced Semiconductor Devices 2008年07月
  • 塩崎奈々子, 佐藤威友, 橋詰保
    応用物理学関係連合講演会講演予稿集 2008年03月
  • 溝畑彰規, 佐藤威友, 橋詰保
    応用物理学関係連合講演会講演予稿集 2008年03月
  • Electrochemical formation and sensor application of highly-ordered InP nanostructures  [通常講演]
    SATO Taketomo, MIZOHATA Akinori, YOSHIZAWA Naoki, HASHIZUME Tamotsu
    2008 RCIQE International Seminar on "Advanced Semiconductor Materials and Devices" 2008年03月
  • 溝畑彰規, 佐藤威友, 橋詰保
    応用物理学会北海道支部・日本光学会北海道支部合同学術講演会講演予稿集 2008年01月
  • 塩崎奈々子, 石川史太郎, TRAMPERT A, GRAHN H. T, 佐藤威友, 橋詰保
    応用物理学会学術講演会講演予稿集 2007年09月
  • 佐藤威友, 溝畑彰規, 橋詰保
    応用物理学会学術講演会講演予稿集 2007年09月
  • 塩崎奈々子, 佐藤威友, 橋詰保
    応用物理学関係連合講演会講演予稿集 2007年03月
  • 佐藤威友, 佐藤威友, 藤野敏幸, 藤野敏幸, 橋詰保, 橋詰保
    応用物理学関係連合講演会講演予稿集 2007年03月
  • 木村健, 佐藤威友, 橋詰保
    応用物理学関係連合講演会講演予稿集 2007年03月
  • Electrochemical formation and optical characterization of size-controlled InP porous nanostructures  [通常講演]
    SATO Taketomo, FUJINO Toshiyuki, HASHIZUME Tamotsu
    The 4th International Symposium on Ubiquitous Knowledge Network Environment, Meme-Media Technology Approach to the R&D of Next-Generation Information Technologies 2007年03月
  • Chemical sensors using open-gate AlGaN/GaN transistor structures  [通常講演]
    KOKAWA Takuya, SATO Taketomo, HASHIZUME Tamotsu
    The 4th International Symposium on Ubiquitous Knowledge Network Environment, Meme-Media Technology Approach to the R&D of Next-Generation Information Technologies 2007年03月
  • Electrochemical formation of high-density array of InP nanostructures  [通常講演]
    SATO TAKATOMO
    2007 RCIQE International Seminar on "Advanced Semiconductor Materials and Devices" 2007年02月
  • Electrochemical Formation and Sensor Application of InP Porous Nanostructures  [通常講演]
    2007 Asia-Pacific Workshop on Fundamentals and Applications of Advanced Semiconductor Devices 2007年
  • Electrochemical Formation of InP Porous Nanostructures and Its Application to Amperometric Chemical Sensors  [通常講演]
    2007 European Materials Research Society Fall Meeting 2007年
  • 藤野敏幸, 佐藤威友, 橋詰保
    応用物理学会学術講演会講演予稿集 2006年08月
  • 塩崎奈々子, 佐藤威友, 橋詰保
    応用物理学会学術講演会講演予稿集 2006年08月
  • 田村隆博, 葛西誠也, 佐藤威友, 橋詰保
    応用物理学会学術講演会講演予稿集 2006年08月
  • 古川拓也, 佐藤威友, 橋詰保
    応用物理学会学術講演会講演予稿集 2006年08月
  • 木村健, 佐藤威友, 橋詰保, 長谷川英機
    応用物理学関係連合講演会講演予稿集 2006年03月
  • 古川拓也, 佐藤威友, 長谷川英機, 橋詰保
    応用物理学関係連合講演会講演予稿集 2006年03月
  • 塩崎奈々子, 佐藤威友, 長谷川英機, 橋詰保
    応用物理学関係連合講演会講演予稿集 2006年03月
  • 佐藤威友, 佐藤威友, 及川武, 及川武, 長谷川英機, 長谷川英機
    応用物理学関係連合講演会講演予稿集 2006年03月
  • 田村隆博, 玉井功, 葛西誠也, 佐藤威友, 長谷川英機, 橋詰保
    応用物理学関係連合講演会講演予稿集 2006年03月
  • 藤野敏幸, 木村健, 佐藤威友, 長谷川英機, 橋詰保
    応用物理学関係連合講演会講演予稿集 2006年03月
  • Optical Properties of Size-controlled Porous Nanostructures Formed on n-InP (001) Substrates by Electrochemical Process  [通常講演]
    FUJINO Toshiyuki, SATO Taketomo, HASHIZUME Tamotsu
    2006 International Conference on Solid State Devices and Materials 2006年
  • Self-assembled Formation of Uniform Arrays of InP Nanopores and Nanowires by Electrochemical Process  [通常講演]
    SATO Taketomo, FUJINO Toshiyuki, HASHIZUME Tamotsu
    210th Meeting of the Electrochemical Society 2006年
  • Self-Assembled Formation of Uniform Arrays of InP Nanopores and Nanowires by Electrochemical Process  [通常講演]
    210th Joint International Meeting of Electrochemical Society 2006年
  • Selective MBE Growth of Shape- Size- and Position- Controlled GaAs Nanowire Networks on (111)B Patterned Substrates  [通常講演]
    TAMAI Isao, SATO Taketomo, HASEGAWA Hideki
    International Semiconductor Device Research Symposium 2005年12月
  • Self-Organized Formation of Chaotic and Regular Nanostructures on (001) and (111) InP Substrates by Electrochemical Anodization Process  [通常講演]
    FUJINO Toshiyuki, KIMURA Takeshi, SATO Taketomo, HASEGAWA Hideki, HASHIZUME Tamotsu
    International Symposium on Surface Science and Nanotechnology 2005年11月
  • Growth Simulation and Actual MBE Growth of Triangular GaAs Nanowires on Patterned (111)B Substrates  [通常講演]
    TAMAI Isao, SATO Taketomo, HASEGAWA Hideki, HASHIZUME Tamotsu
    International Symposium on Surface Science and Nanotechnology 2005年11月
  • Embedded Nanowire Network Growth and Node Device Fabrication for GaAs-Based High-Density Hexagonal BDD Quantum Circuits  [通常講演]
    TAMURA Takahiro, TAMAI Isao, KASAI Seiya, SATO Taketomo, HASEGAWA Hideki, HASHIZUME Tamotsu
    2005 Solid State Devices and Materials 2005年09月
  • Sensing Mechanism of InP Hydrogen Sensors Using Pt Schottky Diodes Formed by Electrochemical Process  [通常講演]
    KIMURA Takeshi, HASEGAWA Hideki, SATO Taketomo, HASHIZUME Tamotsu
    2005 Solid State Devices and Materials 2005年09月
  • 田村隆博, 玉井功, 葛西誠也, 佐藤威友, 長谷川英機, 橋詰保
    応用物理学会学術講演会講演予稿集 2005年09月
  • 及川武, 佐藤威友, 長谷川英機, 橋詰保
    応用物理学会学術講演会講演予稿集 2005年09月
  • 藤野敏幸, 佐藤威友, 長谷川英機, 橋詰保
    応用物理学会学術講演会講演予稿集 2005年09月
  • 佐藤威友, 玉井功, 長谷川英機
    応用物理学会学術講演会講演予稿集 2005年09月
  • 木村健, 佐藤威友, 長谷川英機, 橋詰保
    応用物理学会学術講演会講演予稿集 2005年09月
  • 塩崎奈々子, 佐藤威友, 赤沢正道, 長谷川英機, 橋詰保
    応用物理学会学術講演会講演予稿集 2005年09月
  • 玉井功, 佐藤威友, 長谷川英機, 橋詰保
    応用物理学会学術講演会講演予稿集 2005年09月
  • Precisely Controlled Anodic Etching for Processing of GaAs-based Quantum Nanostructures and Devices  [通常講演]
    SHIOZAKI Nanako, SATO Taketomo, AKAZAWA Masamichi, HASEGAWA Hideki
    10th International Conference on the Formation of Semiconductor Interfaces (ICFSI-10) 2005年07月
  • Selective MBE growth ofAlGaN/GaN quantum wire structures on pre-patterned GaN (0001) substrates and its growth mechanism  [通常講演]
    OIKAWA Takeshi, SATO Taketomo, HASEGAWA Hideki
    8th International Conference on Atomically Controlled Surfaces Interfaces and Nanostructures 2005年06月
  • MBE Growth and Si-interlayer Based Surface Passivation of GaAs Quantum Wires  [通常講演]
    SHIOZAKI Nanako, SATO Taketomo, AKAZAWA Masamichi, HASEGAWA Hideki
    29th Workshop on Compound Semiconductor Devices and Integrated Circuit 2005年05月
  • Electrodeposited Pt/InP Schottky Barriers with Large Barrier Heights and Large Hydrogen Sensitivity for Sensor Chips Using InP-based Quantum Wire Networks  [通常講演]
    KIMURA Takeshi, MATSUO Kazushi, SATO Taketomo, HASHIZUME, Tamotsu, HASEGAWA Hideki
    17th Indium Phosphide and Related Materials Conference 2005年05月
  • 及川武, 佐藤威友, 橋詰保, 長谷川英機
    応用物理学関係連合講演会講演予稿集 2005年03月
  • 田村隆博, 湯元美樹, 玉井功, 葛西誠也, 佐藤威友, 長谷川英機
    応用物理学関係連合講演会講演予稿集 2005年03月
  • 玉井功, 佐藤威友, 長谷川英機
    応用物理学関係連合講演会講演予稿集 2005年03月
  • 塩崎奈々子, 玉井功, 佐藤威友, 長谷川英機
    応用物理学関係連合講演会講演予稿集 2005年03月
  • 佐藤威友, 玉井功, 長谷川英機
    応用物理学関係連合講演会講演予稿集 2005年03月
  • 木村健, 佐藤威友, 長谷川英機
    応用物理学関係連合講演会講演予稿集 2005年03月
  • Growth Kinetics and Theoretical Modeling of Selective Molecular Beam Epitaxy for Growth of GaAs Nanowires on Non-planar Substrates  [通常講演]
    SATO Taketomo, TAMAI Isao, HASEGAWA Hideki
    2005 RCIQE International Seminar for 21st Century COE Program: Quantum Nanoelectronics for Meme-Media-Based Information Technologies (III) 2005年02月
  • Investigation of Side-Gating Effects in GaAs-based Quantum Wire Transistor  [通常講演]
    JIA Rui, KASAI Seiya, SATO Taketomo, HASEGAWA Hideki
    2005 RCIQE International Seminar for 21st Century COE Program: Quantum Nanoelectronics for Meme-Media-Based Information Technologies (III) 2005年02月
  • High-Density Hexagonal Nanowire Networks on Pre-Patterned GaAs (001) and (111)B Substrates by Selective MBE Growth  [通常講演]
    TAMAI Isao, SATO Taketomo, HASEGAWA Hideki
    2005 RCIQE International Seminar for 21st Century COE Program: Quantum Nanoelectronics for Meme-Media-Based Information Technologies (III) 2005年02月
  • Effects of Surface States and Si-interlayer Based Surface Passivation on GaAs Quantum Wires Grown by Selective Molecular Beam Epitaxy  [通常講演]
    SHIOZAKI Nanako, SATO Taketomo, HASEGAWA Hideki
    32nd Conference on the Physics and Chemistry of Semiconductor Interfaces 2005年01月
  • Growth Kinetics and Theoretical Modeling of Selective Molecular Beam Epitaxy for Growth of GaAs Nanowires on Non-planar (111)B Substrates  [通常講演]
    SATO Taketomo, TAMAI Isao, HASEGAWA Hideki
    32nd Conference on the Physics and Chemistry of Semiconductor Interfaces 2005年01月
  • Self-assembled formation of InP nanopore arrays by photoelectrochemical anodization in HCl based electrolyte  [通常講演]
    SATO Taketomo, FUJINO Toshiyuki, HASEGAWA Hideki
    8th International Conference on Atomically Controlled Surfaces Interfaces and Nanostructures 2005年01月
  • Growth of GaN Based Quantum Wire Arrays and Networks by RF Radical Assisted Selective Molecular Beam Epitaxy  [通常講演]
    SATO Taketomo, OIKAWA Takeshi, HASEGAWA Hideki
    The 5th International Conference on Low Dimensional Structures and Devices (LDSD2004) 2004年12月
  • Hexagonal BDD Quantum Circuit Architecture for Intelligent Quantum (IQ) Chips  [通常講演]
    HASEGAWA Hideki, KASAI Seiya, YUMOTO Miki, SATO Taketomo
    11th Advanced Heterostructure Workshop 2004年12月
  • Selective MBE Growth of High-Density Hexagonal Nanowire Networks on Pre-Patterned GaAs (001) and (111)B Substrates International Symposium on Nanoscale Devices and Materials  [通常講演]
    TAMAI Isao, SATO Taketomo, HASHIZUME Tamotsu, HASEGAWA Hideki
    206th Meeting of ECS 2004年10月
  • Design and Implementation of Ultra-Small and Ultra-Low-Power Digital Systems Utilizing A Hexagonal BDD Quantum Circuits on GaAs-based Hexagonal Nanowire Network Structures  [通常講演]
    KASAI Seiya, YUMOTO Miki TAMURA Takahiro, TAMAI Isao, SATO Taketomo, HASEGAWA Hideki
    International Symposium on Nanoscale Devices and Materials:206th Meeting of ECS 2004年10月
  • Molecular Beam Epitaxial Growth of GaAs- and GaN-Based Quantum Wire Arrays and Networks on Pre-Patterned Substrates  [通常講演]
    SATO Taketomo, TAMAI Isao, OIKAWA Takeshi, HASEGAWA Hideki
    7th China-Japan Symposium on Thin Films (CJSTF-7) 2004年09月
  • Growth of AlGaN/GaN Quantum Wire Structures by RF-Radical Assisted MBE on Pre-Patterned Substrates  [通常講演]
    SATO Taketomo, OIKAWA Takeshi, HASHIZUME Tamotsu, HASEGAWA Hideki
    International Conference on Solid State Devices and Materials 2004 2004年09月
  • Cross-sectional Evolution and Its Mechanism during Selective MBE Growth of GaAs Quantum Wires on (111)B Substrates  [通常講演]
    TAMAI Isao, SATO Taketomo, HASEGAWA Hideki
    International Conference on Solid State Devices and Materials 2004 2004年09月
  • Investigation of Current and Potential Control Characteristics by Nanosized Schottky Gate on AlGaAs/GaAs Surfaces  [通常講演]
    JIA Rui, SATO Taketomo, KASAI Seiya, HASEGAWA Hideki
    31st International Symposium on Compound Semiconductors 2004年09月
  • Investigation of Current and Potential Control Characteristics by Nanosized Schottky Gate on AlGaAs/GaAs Surfaces  [通常講演]
    Jia Rui, Sato Taketomo, Kasai Seiya, Hasegawa Hideki
    応用物理学会学術講演会講演予稿集 2004年09月
  • 玉井功, 佐藤威友, 長谷川英機
    応用物理学会学術講演会講演予稿集 2004年09月
  • 木村健, 佐藤威友, 長谷川英機
    応用物理学会学術講演会講演予稿集 2004年09月
  • 塩崎奈々子, 佐藤威友, 橋詰保, 長谷川英機
    応用物理学会学術講演会講演予稿集 2004年09月
  • 及川武, 佐藤威友, 橋詰保, 長谷川英機
    応用物理学会学術講演会講演予稿集 2004年09月
  • 田村隆博, 湯元美樹, 玉井功, 佐藤威友, 葛西誠也, 長谷川英機
    応用物理学会学術講演会講演予稿集 2004年09月
  • 佐藤威友, 及川武, 橋詰保, 長谷川英機
    応用物理学会学術講演会講演予稿集 2004年09月
  • Selective MBE Growth of GaAs Hexagonal Nano-wire Network on Pre-patterned Substrates  [通常講演]
    TAMAI Isao, SATO Taketomo, HASEGAWA Hideki
    Hokkaido Univ. and Seoul National Univ. Joint Symposium 2004年07月
  • Growth Mechanism of GaAs Ridge Quantum Wires on Patterned Substrates  [通常講演]
    SATO Taketomo, TAMAI Isao, HASEGAWA Hideki
    Hokkaido Univ. and Seoul National Univ. Joint Symposium 2004年07月
  • Sidegating Effect Study in AlGaAs/GaAs Quantum Wire Transistors  [通常講演]
    JIA Rui, KASAI Seiya, SATO Taketomo, HASEGAWA Hideki
    Hokkaido Univ. and Seoul National Univ. Joint Symposium 2004年07月
  • GaAs BDD Quantum Node Switches Fabricated on Selectively MBE Grown Quantum Wire Networks  [通常講演]
    TAMURA Takahiro, YUMOTO Miki, KASAI Seiya, SATO Taketomo, HASEGAWA Hideki
    46th Electronic Materials Conference (EMC2004) 2004年06月
  • Controlled growth of GaAs ridge quantum wire network by selective MBE and its application to hexagonal BDD quantum logic circuits  [通常講演]
    HASEGAWA Hideki, SATO Taketomo, TAMURA Takahiro, TAMAI Isao, YUMOTO Miki
    12th Int. Symposium on Nanostructures Physics and Technology 2004年06月
  • Surface-related reduction of photoluminescence from GaAs quantum wires and effects of surface passivation using Si interface control layer  [通常講演]
    SHIOZAKI Nanako, ANANTATHANASARN Sanguan, SATO Taketomo, HASHIZUME Tamotsu, HASEGAWA Hideki
    The 12th International Conference on Solid Films and Surfaces 2004年06月
  • Study on ECR dry etching and selective MBE growth of AlGaN/GaN for fabrication of quantum nanostructures on GaN(0001) substrates  [通常講演]
    OIKAWA Takeshi, ISHIKAWA Fumitaro, SATO Taketomo, HASHIZUME Tamotsu, HASEGAWA Hideki
    The 12th International Conference on Solid Films and Surfaces 2004年06月
  • 田村隆博, 湯元美樹, 玉井功, 佐藤威友, 葛西誠也, 長谷川英機
    応用物理学関係連合講演会講演予稿集 2004年03月
  • 佐藤威友, 玉井功, 長谷川英機
    応用物理学関係連合講演会講演予稿集 2004年03月
  • 玉井功, 吉田崇一, 佐藤威友, 長谷川英機
    応用物理学関係連合講演会講演予稿集 2004年03月
  • 吉田崇一, 玉井功, 佐藤威友, 長谷川英機
    応用物理学関係連合講演会講演予稿集 2004年03月
  • 石川史太郎, 及川武, 玉井功, 佐藤威友, 長谷川英機
    応用物理学関係連合講演会講演予稿集 2004年03月
  • Growth Kinetics and Modeling of Selective Molecular Beam Epitaxial Growth of GaAs Ridge Quantum Wires on Pre-Patterned Substrates  [通常講演]
    SATO Taketomo, TAMAI Isao, HASEGAWA Hideki
    2004 International Seminar for 21st Century COE Program: Quantum Nanoelectronics for Meme-Media-Based Infromation Technology (II) 2004年02月
  • Mechanism of Selective Growth of GaAs Ridge Quantum Wires on Non-planar Substrates during Molecular Beam Epitaxy  [通常講演]
    SATO Taketomo, TAMAI Isao, HASEGAWA Hideki
    31st Conference on the Physics and Chemistry of Semiconductor Interfaces 2004年01月
  • Prospects of III-V quantum LSIs based on hexagonal BDD approach  [招待講演]
    KASAI Seiya, SATO Taketomo, HASEGAWA Hideki
    2003年12月
  • Selective MBE Growth of GaAs Hexagonal Nano-wire Networks on (111)B Patterned Substrates  [通常講演]
    YOSHIDA Souichi, TAMAI Isao, SATO Taketomo, HASEGAWA Hideki
    International Conference on Solid State Devices and Materials 2003年09月
  • Control of Heterointerface Cross-Sections of GaAs Ridge Quantum Wires by Selective Molecular Beam Epitaxy  [通常講演]
    SATO Taketomo, TAMAI Isao, YOSHIDA Souichi, HASEGAWA Hideki
    The 9th International Conference on the Formation of Semiconductor Interfaces (ICFSI-9) 2003年09月
  • 玉井功, 吉田崇一, 佐藤威友, 長谷川英機
    応用物理学会学術講演会講演予稿集 2003年08月
  • 吉田崇一, 玉井功, 佐藤威友, 長谷川英機
    応用物理学会学術講演会講演予稿集 2003年08月
  • 佐藤威友, 玉井功, 吉田崇一, 長谷川英機
    応用物理学会学術講演会講演予稿集 2003年08月
  • Formation of High Density GaAs Hexagonal Nanowire Networks by Selective MBE Growth on Pre-patterned (001) Substrates  [通常講演]
    TAMAI Isao, SATO Taketomo, HASEGAWA Hideki
    11th International Conference on Modulated Semiconductor Structures (MSS11) 2003年07月
  • Kinetic Evolution of Facet Boundary Planes during Growth of III-V Ridge Quantum Wire Arrays by Selective Molecular Beam Epitaxy  [通常講演]
    HASEGAWA Hideki, SATO Taketomo, JIANG Chao, MURANAKA Tsutomu
    Symposium on Surface Science 2003 (3S03) 2003年03月
  • 玉井功, 吉田崇一, 佐藤威友, 長谷川英機
    応用物理学関係連合講演会講演予稿集 2003年03月
  • 吉田崇一, 玉井功, 佐藤威友, 長谷川英機
    応用物理学関係連合講演会講演予稿集 2003年03月
  • 佐藤威友, 玉井功, 長谷川英機
    応用物理学関係連合講演会講演予稿集 2003年03月
  • Selective MBE Growth of GaAs Ridge Quantum Wires for Formation of Hexagonal Nanowire Networks  [通常講演]
    SATO Taketomo, TAMAI Isao, HASEGAWA Hideki
    2003 RCIQE International Seminar on Quantum Nanoelectronics for Meme-Media-Based Information Technologies 2003年02月
  • Selective MBE Growth of GaAs Ridge Quantum Wire Arrays on Patterned (001) Substrates and Its Growth Mechanism  [通常講演]
    SATO Taketomo, TAMAI Isao, HASEGAWA Hideki
    29th International Symposium on Compound Semiconductors (ISCS2002) 2002年10月
  • 亀田篤志, 葛西誠也, 佐藤威友, 長谷川英機
    応用物理学会学術講演会講演予稿集 2002年09月
  • 佐藤威友, 玉井功, 長谷川英機
    応用物理学会学術講演会講演予稿集 2002年09月
  • 玉井功, 吉田崇一, 佐藤威友, 長谷川英機
    応用物理学会学術講演会講演予稿集 2002年09月
  • Selective MBE Growth of <-110> and <510>-Oriented GaAs Ridge Quantum Wires on Patterned (001) Substrates for Formation of Hexagonal Nanowire Networks  [通常講演]
    SATO Taketomo, TAMAI Isao, HASEGAWA Hideki
    The Second International Workshop on Quantum Nonplanar Nanostructures & Nanoelectronics (QNN02) 2002年09月
  • Mechanism and Suppression of Anomalously Large Reverse Leakage Currents in n-type GaN Schottky Contacts  [通常講演]
    SATO Taketomo, OYAMA Susumu, HASEGAWA Hideki
    26th International Conference on the Physics of Semiconductors 2002年07月
  • Selective MBE Growth of High Density GaAs/AlGaAs Hexagonal Nanowire Network Structures on Pre-Patterned GaAs Substrates  [通常講演]
    TAMAI Isao, SATO Taketomo, HASEGAWA Hideki
    2002 Electronic Materials Conference 2002年06月
  • Understanding and Control of Current Transport in GaN Schottky Contacts with Large Reverse Leakage Currents  [通常講演]
    HASEGAWA Hideki, SATO Taketomo, OYAMA Susumu
    26th Workshop on Compound Semiconductor Devices and Integrated Circuits held in Europe (WOCSDICE) 2002年05月
  • 玉井功, 佐藤威友, 長谷川英機
    応用物理学関係連合講演会講演予稿集 2002年03月
  • 亀田篤志, 葛西誠也, 佐藤威友, 長谷川英機
    応用物理学関係連合講演会講演予稿集 2002年03月
  • 平野哲郎, 佐藤威友, 長谷川英機
    応用物理学関係連合講演会講演予稿集 2002年03月
  • 佐藤威友, 玉井功, 長谷川英機
    応用物理学関係連合講演会講演予稿集 2002年03月
  • 平野哲郎, 佐藤威友, 伊藤章, 石川史太郎, 長谷川英機
    応用物理学会学術講演会講演予稿集 2001年09月
  • 佐藤威友, 玉井功, 長谷川英機
    応用物理学会学術講演会講演予稿集 2001年09月
  • 平野哲郎, 佐藤威友, 伊藤章, 石川史太郎, 長谷川英機
    応用物理学関係連合講演会講演予稿集 2001年03月
  • 佐藤威友, 亀田篤志, 葛西誠也, 長谷川英機
    応用物理学関係連合講演会講演予稿集 2001年03月
  • Effects of Surface Fermi Level Pinning and Surface State Charging on Control Characteristics of Nanometer Scale Schottky Gates Formed on GaAs  [通常講演]
    KAMEDA Atsuchi, KASAI Seiya, SATO Taketomo, HASEGAWA Hideki
    2001 International Semiconductor Device Research Symposium (ISDRS2001) 2001年
  • Selective MBE Growth of GaAs/AlGaAs Hexagonal Nanowire Network Structures on (001) Patterned GaAs Substrates  [通常講演]
    SATO Taketomo, TAMAI Isao, JIANG Chao, HASEGAWA Hideki
    28th International Symposium on Compound Semiconductors (ISCS2001) 2001年
  • Electrochemical Formation of Self-Assembled Nanopore Arrays As Templates for MBE Growth of InP-based Quantum Wires and Dots  [通常講演]
    HIRANO Tetsuro, ITO Akira, SATO Taketomo, ISHIKAWA Fumitaro, HASEGAWA Hideki
    2001 International Conference on Indium Phosphide and Related Materials (IPRM2001) 2001年
  • 岡田浩, 佐藤威友, 長谷川英機
    応用物理学会学術講演会講演予稿集 2000年09月
  • 佐藤威友, 葛西誠也, 長谷川英機
    応用物理学会学術講演会講演予稿集 2000年09月
  • 岡田浩, 佐藤威友, 長谷川英機
    応用物理学関係連合講演会講演予稿集 2000年03月
  • 佐藤威友, 葛西誠也, 岡田浩, 長谷川英機
    応用物理学関係連合講演会講演予稿集 2000年03月
  • Electrical Properties of Nanometer-Sized Schottky Contacts for Gate Control of III-V Single Electron Devices  [通常講演]
    SATO Taketomo, KASAI Seiya, HASEGAWA Hideki
    International Symposium on Formation Physics and Device Application of Quantum Dot Structures 2000年
  • Current Transport and Capacitance-Voltage Characteristics of GaAs and InP Nanometer-Sized Schottky Contacts Formed by in situ Electrochemical Process  [通常講演]
    SATO Taketomo, KASAI Seiya, HASEGAWA Hideki
    10 th International Conference on Solid Films and Surfaces 2000年
  • Formation and Characterization of Nanometer-Sized Schottky Contacts on III-V Materials by In-SItu Electrochemical Process  [通常講演]
    SATO Taketomo, KASAI Seiya, HASEGAWA Hideki
    42nd Electronic Materials Conference 2000年
  • Self-Assembled Formation of InP Nanopore Arrays by Electrochemical Anodization  [通常講演]
    FUJIKURA Hajime, LIU Aimin, SATO Taketomo, HIRANO Tetsuro, HASEGAWA Hideki
    2000 International Conference on Indium Phosphide and Related Materials (IPRM2000) 2000年
  • 佐藤威友, 葛西誠也, 岡田浩, 長谷川英機
    電気関係学会北海道支部連合大会講演論文集 1999年10月
  • 岡田浩, 佐藤威友, 長谷川英機
    応用物理学会学術講演会講演予稿集 1999年09月
  • 佐藤威友, 葛西誠也, 岡田浩, 長谷川英機
    応用物理学会学術講演会講演予稿集 1999年09月
  • 岡田浩, 佐藤威友, 長谷川英機
    応用物理学関係連合講演会講演予稿集 1999年03月
  • 佐藤威友, 岡田浩, 長谷川英樹
    応用物理学関係連合講演会講演予稿集 1999年03月
  • 橋詰保, 兼城千波, 佐藤威友, 長谷川英機
    電気化学会大会講演要旨集 1999年03月
  • Properties of nanometer-sized metal contacts on GaAs, InP and their related materials  [通常講演]
    HASEGAWA Hideki, SATO Taketomo, KASAI Seiya
    Surfaces and Interfaces of Mesoscopic Devices 1999年
  • Electrochemical Formation of Nanometer-Sized Straight Pore Arrays on (001) InP Surfaces  [通常講演]
    LIU Aimin, HAMAMATSU Akihito, SATO Taketomo, FUJIKURA Hajime, HASEGAWA Hideki
    International Symposium on Surface Science for Micro- and Nano-Device Fabrication 1999年
  • Electrical Properties of Nanometer-Sized Schottky Contacts on n-GaAs and n-InP Formed by in situ Electrochemical Process  [通常講演]
    SATO Taketomo, KASAI Seiya, OKADA Hiroshi, HASEGAWA Hideki
    International Symposium on Surface Science for Micro- and Nano-Device Fabrication 1999年
  • Unpinning of Fermi Level in Nanometer-Sized Schottky Contacts on GaAs and InP  [通常講演]
    HASEGAWA Hideki, SATO Taketomo
    7th International Conference on Formation of Semiconductor Interfaces 1999年
  • Subnano-Scale Selective Etching and Nano-Scale Pore Array Formation on InP (001) Surfaces by a Wet Electrochemical Process  [通常講演]
    HAMAMATSU Akihito, KANESHIRO Chinami, SATO Taketomo, FUJIKURA Hajime, HASEGAWA Hideki
    International Conference on 1999 Indium Phosphide and Related Materials (IPRM99) 1999年
  • Formation on Nanometer-Sized Schottky Contacts on InP and Related Materials by in situ Electrochemical Process  [通常講演]
    SATO Taketomo, OKADA Hiroshi, HASEGAWA Hideki
    11th International Conference on Indium Phosphide and Related Materials (IPRM99) 1999年
  • Formation of Fermi Level Pinning Free Nano-scale Schottky Contacts on Compound Semiconductor and Their Application to Single Electron Devices  [通常講演]
    HASEGAWA Hideki, SATO Taketomo, OKADA Hiroshi
    Symposium on Surface Physics 1999年
  • 岡田浩, 佐藤威友, 兼城千波, 地主啓一郎, 長谷川英機
    応用物理学会学術講演会講演予稿集 1998年09月
  • 浜松亮仁, 佐藤威友, 兼城千波, 藤倉序章, 長谷川英機
    応用物理学会学術講演会講演予稿集 1998年09月
  • 兼城千波, 佐藤威友, 橋詰保, 長谷川英機
    応用物理学会学術講演会講演予稿集 1998年09月
  • 佐藤威友, 岡田浩, 兼城千波, 長谷川英機
    応用物理学会学術講演会講演予稿集 1998年09月
  • 佐藤威友, 岡田浩, 兼城千波, 長谷川英機
    応用物理学関係連合講演会講演予稿集 1998年03月
  • 兼城千波, 佐藤威友, 橋詰保, 長谷川英機
    応用物理学関係連合講演会講演予稿集 1998年03月
  • 浜松亮仁, 兼城千波, 佐藤威友, 長谷川英機
    応用物理学関係連合講演会講演予稿集 1998年03月
  • 佐藤威友, 兼城千波, SOKOLOV D V, 橋詰保, 長谷川英機
    応用物理学関係連合講演会講演予稿集 1998年03月
  • Properties of Nanometer-Sized Metal-Semiconductor Interfaces of GaAs, InP and GaN Formed by An In-Situ Electrochemical Process  [通常講演]
    HASEGAWA Hideki, SATO Taketomo, KANESHIRO Chinami, KOYAMA Yuuji
    1999 International Conference on Physics and Chemistry of Semiconductor Interfaces 1998年
  • Realization of Strongly Metal-Dependent Schottky Barrier Heights on n-GaAs by In Situ Electrochemical Process  [通常講演]
    KANESHIRO Chinami, SATO Taketomo, HASHIZUME Tamotsu, HASEGAWA Hideki
    25th International Symposium on Compound Semiconductors 1998年
  • Surface Modification of InP By Photoelectrohcemical Process  [通常講演]
    HAMAMATSU Akihito, KANESHIRO Chinami, SATO Taketomo, FUJIKURA Hajime, HASEGAWA Hideki
    International Symposium on Electrochemistry of Ordered Interfaces 1998年
  • Formation of Size- and Position-Controlled Nanometer Size Pt Dots on GaAs and InP Substrates by Pulsed Electrochemical Deposition  [通常講演]
    SATO Taketomo, KANESHIRO Chinami, OKADA Hiroshi, HASEGAWA Hideki
    International Conference on Solid State Devices and Materials 1998年
  • Fabrication of Regular Arays of Nanometer-Sized Pt Dots on III-V Substrates by Electron Beam Lithography and Electrochemical Deposition  [通常講演]
    SATO Taketomo, KANESHIRO Chinami, OKADA Hiroshi, HASEGAWA Hideki
    40th Electronic Matterials Conference (EMC'98) 1998年
  • Highly Controllable Electrochemical Etching of InP studied by Voltammetry and Scanned Probe Microscope  [通常講演]
    KANESHIRO Chinami, SATO Taketomo, HASEGAWA Hideki
    10th International Conference on Indium Phosphide and Related Materials (IPRM98) 1998年
  • Strong Correlation Between Interface Microstructure and Barrier Height in n-InP Schottky Contacts Formed by In Situ Electrochemical Process  [通常講演]
    SATO Taketomo, KANESHIRO Chinami, HASEGAWA Hideki
    10th International Conference on Indium Phosphide and Related Materials (IPRM98) 1998年
  • 佐藤威友, 岡田浩, 兼城千波, 長谷川英機
    電気関係学会北海道支部連合大会講演論文集 1998年
  • 兼城千波, 佐藤威友, 橋詰保, 長谷川英機
    応用物理学会学術講演会講演予稿集 1997年10月
  • 浜松亮仁, 佐藤威友, 兼城千波, 斎藤俊也, 橋詰保, 長谷川英機
    応用物理学会学術講演会講演予稿集 1997年10月
  • 佐藤威友, 兼城千波, 橋詰保, 長谷川英機
    応用物理学会学術講演会講演予稿集 1997年10月
  • 佐藤威友, 橋詰保, 長谷川英機
    電気化学秋季大会講演要旨集 1997年08月
  • 野矢厚, 武山真弓, 佐藤威友, 橋詰保, 長谷川英機
    応用物理学関係連合講演会講演予稿集 1997年03月
  • 佐藤威友, 橋詰保, 長谷川英機
    応用物理学関係連合講演会講演予稿集 1997年03月
  • Formation of Pinning-Free Schottky Barriers on InP and Related Materials by Novel In-Situ Electrochemical Process and Its Mechanism  [通常講演]
    SATO Taketomo, HASEGAWA Hideki
    9th International Conference on Indium Phosphide and Related Materials (IPRM97) 1997年
  • Evolution of Nearly Pinning-Free Metal-Semiconductor Interfaces on InP and Related Materials by Novel In-Situ Electrochemical Process  [通常講演]
    SATO Taketomo, HASHIZUME Tamotsu, HASEGAWA Hideki
    1997 International Conference on Physics and Chemistry of Semiconductor Interfaces 1997年
  • 兼城千波, 佐藤威友, 橋詰保, 長谷川英機
    電気関係学会北海道支部連合大会講演論文集 1997年
  • 佐藤威友, 兼城千波, 橋詰保, 長谷川英機
    電気関係学会北海道支部連合大会講演論文集 1997年
  • 佐藤威友, 宇野正一, 橋詰保, 長谷川英機
    応用物理学会学術講演会講演予稿集 1996年09月
  • 宇野正一, 佐藤威友, 葛西誠也, 橋詰保, 長谷川英機
    応用物理学関係連合講演会講演予稿集 1996年03月
  • Enhancement of Schottky Barrier Heights on Indium Phosphide-Based Materials by In-Situ Electrochemical Process and Its Mechanism  [通常講演]
    SATO Taketomo, UNO Shouichi, HASHIZUME Tamotsu, HASEGAWA Hideki
    International Conference on Solid State Devices and Materials 1996年
  • Fabrication of high-performance InP MESFETs with in-situ pulse-plated metal gates  [通常講演]
    UNO Shouichi, Tamotsu Hashizme, SATO Taketomo, FUJIKURA Hajime, HASEGAWA Hideki
    International Conference on Indium Phosphide and Related Materials (IPRM96) 1996年
  • 佐藤威友, 橋詰保, 長谷川英機
    電気関係学会北海道支部連合大会講演論文集 1996年

作品等

  • 電子情報工学実験 テキストの作成・更新
    佐藤 威友
  • 量子集積エレクトロニクス研究センター ホームページの更新
    佐藤 威友

その他活動・業績

特許

受賞

  • 2000年11月 応用物理学会 第61回秋期応用物理学会学術講演会『講演奨励賞』
     化合物半導体ナノショットキー界面の電気的特性とその制御 
    受賞者: 佐藤 威友
  • 1997年12月 電気関係学会北海道支部会 平成9年度『若手講演者賞』
     In situ 電気化学プロセスを用いたショットキー障壁の形成 
    受賞者: 佐藤 威友

共同研究・競争的資金等の研究課題

  • 超ワイドギャップAlN系半導体を用いたパワートランジスタの開発
    日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2021年04月 -2024年03月 
    代表者 : 三好 実人, 佐藤 威友
  • 強力な酸化剤を用いた窒化物半導体ウェットエッチング技術の開発とトランジスタ応用
    日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2020年04月 -2023年03月 
    代表者 : 佐藤 威友, 三好 実人, 橋詰 保
  • 特異構造を含む異種接合の界面制御と電子デバイス展開
    日本学術振興会:科学研究費助成事業 新学術領域研究(研究領域提案型)
    研究期間 : 2016年06月 -2021年03月 
    代表者 : 橋詰 保, 赤澤 正道, 佐藤 威友
     
    種々の特異構造を内包するGaN系異種接合界面電気的評価を行い、化学的・構造的・光学的評価と連携させて電子捕獲準位の成因を理解し、混晶異種接合に立脚した新機能素子の実現に貢献する。本年度の主な成果を以下にまとめる。
    1)SiO2およびSiNを保護膜とするGaN試料に、N2中1150℃で1分間のアニールを行い、その後HF溶液により保護膜除去を行った。そのGaN表面に原子層堆積法でAl2O3膜を形成した。CV特性の評価より、Al2O3/GaN界面に高密度の電子捕獲準位が存在することが示されたが、SiO2保護膜の場合、400℃/10分のPMA(post-metallization annealing)で顕著な界面特性の回復が観測された。一方、SiN保護膜の場合はGaN表面にSiNが残存するため(1nm以下)、界面特性回復が不十分であることが明らかになった。 2)光電気化学エッチングは低損傷の特長を持つが、電子-正孔分離用のバイアス印加が必要であった。最近、強力酸化剤のペルオキソ硫酸カリウムを利用することにより、無バイアス(通電電極なし)でGaNのエッチングが可能であることを見出した。このプロセスをAlGaN/GaNヘテロ構造に適用し、無バイアスでAlGaN層の選択的エッチングを行い、エッチング面の良好な平坦性を確認した(RMS値0.24nm)。 3)GaN基板上に成長されたAlGaN/GaN構造に原子層堆積法でAl2O3ゲートを形成し、その電気的評価を行った。PMA処理を行うことで非常に良好な電流-電圧特性が観測され、サブシュレショルド領域で理論値に近いSS値(68mV/dec)が得られた。さらに高温領域で動作安定性が確認され、150℃動作においても非常に低い漏れ電流(1.5nA/mm)と室温からのしきい値電圧変動も極めて小さい(0.25V)ことが明らかになった。
  • 省エネルギー社会の実現に資する次世代半導体研究開発(パワーデバイス・システム領域)
    文部科学省:委託事業-再委託機関
    研究期間 : 2016年 -2021年
  • 社会実装を目指したGaN縦型パワーデバイス作製技術の確立
    文部科学省:革新的パワーエレクトロニクス創出基盤技術開発事業(パワーデバイス領域)
    研究期間 : 2021年
  • GaNの光電気化学エッチングに関する研究
    株式会社サイオクス:共同研究
    研究期間 : 2021年
  • GaNの光電気化学プロセス
    三菱電機株式会社:共同研究
    研究期間 : 2021年
  • 日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2017年04月 -2020年03月 
    代表者 : 佐藤 威友, 本久 順一, 橋詰 保
     
    光電気化学反応を利用したAlGaN/GaN 高電子移動度トランジスタ(HEMT)のゲートリセス加工プロセスを開発した。溶液とAlGaN界面でおこる反応の基礎過程を明らかにし、AlGaN層で光励起される正孔を利用することにより、平坦でかつ深さ制御されたエッチングが可能であることを見出した。さらに最適な反応条件では、エッチングが自己停止することを発見し、チップ面内において均一な深さで加工を止める方法を確立した。これにより作製されたショットキー型およびMIS型HEMTは、従来素子と比べて、しきい値電圧のばらつきが小さく、ゲート制御性が向上することを示した。
  • 自己停止酸化機構を利用した窒化物半導体低損傷加工プロセスの開発とトランジスタ応用
    文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 2017年04月 -2020年03月 
    代表者 : 佐藤 威友
  • GaNの光電気化学エッチングに関する研究
    株式会社サイオクス:共同研究
    研究期間 : 2020年
  • GaNの光電気化学プロセス
    三菱電機株式会社:共同研究
    研究期間 : 2020年
  • GaNの光電気化学エッチングに関する研究
    株式会社サイオクス:共同研究
    研究期間 : 2019年
  • 日本学術振興会:科学研究費助成事業 挑戦的萌芽研究
    研究期間 : 2015年04月 -2018年03月 
    代表者 : 佐藤 威友, 橋詰 保, 本久 順一
     
    電気化学的手法により形成される「多孔質構造」を基盤とした窒化ガリウム(GaN)光触媒電極の開発に取り組んだ。電気化学エッチング条件およびその後の化学エッチング条件により、多孔質構造の孔径および深さの精密制御を達成した。光反射率低減および表面積増大により、光電気化学変換効率が向上することを明らかにした。さらに、酸化ニッケル(NiO)および酸化銅(Cu2O)によるGaN電極の機能修飾が、それぞれ、腐食耐性の向上と可視光(400-600nm)領域における光電気化学変換に有望であることを示した。
  • 窒化物半導体周期的ナノ構造を基盤とした可視光応答型光触媒の開発と人工光合成応用
    文部科学省:科学研究費補助金(挑戦的萌芽研究)
    研究期間 : 2015年04月 -2018年03月 
    代表者 : 佐藤 威友
  • III-V族化合物半導体の酸化腐食に関する研究
    オルガノ株式会社:共同研究
    研究期間 : 2015年 -2018年
  • 低損傷プロセスによる窒化物半導体表面のナノスケール制御と高感度化学センシング
    文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 2013年04月 -2016年03月 
    代表者 : 佐藤 威友
  • 絶縁膜物性・界面状態のGaNトランジスタの性能と関係性の研究
    住友電気工業株式会社:共同研究
    研究期間 : 2016年 -2016年
  • 文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 2013年 -2015年 
    代表者 : 佐藤 威友
  • GaN HEMTのためのプロセス技術と接合界面評価
    トヨタ自動車株式会社:共同研究
    研究期間 : 2012年 -2015年
  • 日本学術振興会:科学研究費助成事業 挑戦的萌芽研究
    研究期間 : 2012年04月 -2014年03月 
    代表者 : 本久 順一, 佐藤 威友
     
    本研究ではまずRF支援分子線エピタキシー法を用いた選択成長法により、GaNおよびInGaN系ナノ構造の形成を試みた。6角柱錐形状のGaNナノ構造の形成に成功するとともに、選択成長用のマスク材料の変更によりナノワイヤが形成される可能性を示した。続いて、GaNの基本的な電気化学的特性を明らかにするとともに、光支援電気化学エッチングを用いて作製したGaN多孔質構造において、加工前の平坦GaN基板と比較し大きな光電流が流れることを明らかにした。以上により水素発生用材料としてのGaNナノ構造の有望性を示した。
  • 半導体ナノワイヤを基盤とする水素発生用材料の開拓
    文部科学省:科学研究費補助金(挑戦的萌芽研究)
    研究期間 : 2012年 -2014年 
    代表者 : 本久 順一
  • 文部科学省:科学研究費補助金(若手研究(A))
    研究期間 : 2009年 -2012年 
    代表者 : 佐藤 威友
     
    平成21年度は、InPポーラス構造の光学物性・電気伝導特性を明らかにするとともに、ポーラス構造を検出部に有するFET型化学センサの実現に向けた基礎的検討を行った。主たる成果を以下に示す。1.p形InP基板にエピタキシャル成長したn形InP層にポーラス構造を形成し、その電気化学的形成条件を最適化した。孔の形状および孔径は、n形層のドーピング濃度と印加陽極電圧に強く依存することを明らかにし、リソグラフィ技術を用いることなく50nm~700nmの任意の孔径をもつポーラス構造の形成に成功した。また、孔の深さは形成時の通過電荷量に比例することを明らかにし、孔の深さをプロセス時間により精密に制御する手法を確立した。2.pn接合InP基板に作製したポーラス構造の光学的特性・電気伝導特性を、紫外可視分光法・光電流一電圧測定により明らかにした。ポーラス形成初期に形成される表面の不均一層を除去した試料では、極めて低い光反射率と高い光吸収率を示すことを明らかにした。また、ポーラス構造の上面と基板裏面に形成した2電極間の電流-電圧特性は整流性を示し、孔壁において十分な電気伝導度を有するとともに、pn接合の内蔵電位がポーラス形成後も保たれていることを明らかにした。上記1.および2.より、高感度化学センサの基礎構造の1つであるpn接合ポーラス構造が達成され、本研究課題の実現に向けた有望な成果が得た。3....
  • 文部科学省:科学研究費補助金(基盤研究(A))
    研究期間 : 2009年 -2012年 
    代表者 : 橋詰 保, 古賀 裕明, 久保 俊晴, 佐藤 威友, 赤澤 正道
     
    窒化物半導体ヘテロ界面を利用した高電子移動度トランジスタ(HEMT)の劣化特性と表面・バルク電子準位との相関、表面・バルク電子準位の特性解明、電子準位制御構造の開発、新しく提案する多重台形チャネル構造の適用と評価を通して、真にロバストな窒化物半導体トランジスタ構造技術の構築を目的として研究を展開した。本年度の主な成果を以下にまとめる。1)2つのゲートを有するAlGaN/GaN HEMTを用いて、オフ状態電界ストレス後に生じる電流減少(コラプス)を詳細に評価し、ゲート端からの電子注入による表面帯電はドレインおよびソース側の両方向で生じていることを初めて明らかにした。また、多重台形チャネルAlGaN/GaN HEMTにおいては、チャネルインピーダンスが非常に高いため、この表面帯電による寄生抵抗増加の影響が非常に小さく、電流コラプスが生じにくいことがわかった。2)原子層堆積により形成したAl_2O_3/AlGaN/GaN構造に、詳細な計算解析とバンドギャップ以下のエネルギーを持つ光支援測定法を適用し、Al_2O_3/AlGaN界面には1x10^<12>cm^<-2>eV^<-1>以上の密度を持つ電子準位が存在することを初めて明らかにした。3)AlGaN/GaN構造に選択電気化学酸化を適用し、ドライエッチングを用いずにリセス構造+MOSゲート構造を形成した。このプロセスにより、ノーマ...
  • 文部科学省:科学研究費補助金(挑戦的萌芽研究)
    研究期間 : 2009年 -2010年 
    代表者 : 佐藤 威友, 橋詰 保, 本久 順一, 古賀 裕明
     
    平成22年度は、n形インジウムリン(InP)ポーラス(多孔質)構造の内壁に白金(Pt)薄膜を形成する手法を開発し、InP配列ナノ構造を基盤とするPt/InPショットキー型光電変換素子の試作を行った。1.n形InP多孔質構造の孔内壁表面にPt薄膜を電解析出により形成する手法を開発した。真空蒸着法と比較してPt薄膜による孔内壁表面の被覆率が高く、Pt薄膜の厚さは時間により制御可能であることを明らかにした。特に電解析出電圧をパルス波形で印加することにより、膜厚の緻密な制御が可能であり、孔径600nmで深さ4μmからなる多孔質構造の内壁に厚さ20nmの均一なPt薄膜の形成に成功した。2.作製したPt/InP多孔質構造の光反射率特性を明らかにした。入射光200nm-1100nmの波長領域における光反射率は5%以下であり、平坦なInP基板と比較して表面反射が10分の1に低減されていることを明らかにした。3.作製したPt/InP多孔質構造の電気的特性を明らかにした。上部(Pt側)と下部(InP側)に電極を形成して測定した電流・電圧特性が整流性を示すことを明らかにし、Pt/InP多孔質構造の界面にショットキー障壁が形成されていることを確認した。また、光照射下では、光強度に応じて逆方向電流が増大することを明らかにした。この増加電流は、比較用に作製したPt/プレーナInP接合と比べて2~3桁大き...
  • 文部科学省:科学研究費補助金(特定領域研究)
    研究期間 : 2009年 -2010年 
    代表者 : 橋詰 保, 古賀 裕明, 佐藤 威友
     
    AlGaNおよびAlInGaNのバルク欠陥準位と表面・端面における表面電子準位を系統的に評価し、その理解を基盤として、短波長光学素子の高効率化・動作安定化のための電子準位制御法を構築することを目的として研究を展開した。本年度の主な成果を以下にまとめる。1)減圧有機金属気相法により成長したn-AlGaN(膜厚:1μm、Al組成:25、37、60%)の深い準位を評価し、伝導帯下端より1eV以上のエネルギーを持つ電子準位を検出した。支配的準位エネルギーのAl組成依存性は、フェルミ準位安定化エネルギーの計算値に良く追従することを明らかにし、逆位置欠陥と空孔欠陥ペアの複合型欠陥が深い準位の成因である可能性を指摘した。2)原子層堆積により形成したAl_2O_3/AlGaN/GaN構造に、詳細な計算解析とバンドギャップ以下のエネルギーを持つ光支援測定法を適用し、その容量-電圧特性を評価した。その結果、Al_2O_3/AlGaN界面には1x10^<12>cm^<-2>eV^<-1>以上の密度を持つ電子準位が存在することを初めて明らかにした。3)AlGaN表面に電気化学酸化法を適用し、平坦で均一性の高い母体酸化膜を形成することができた。形成した酸化膜の組成は母体AlGaNの組成とほぼ同等であることが分かり、この手法によりAlGaNの表面準位密度を低減できることを明らかにした。また、プロセスによ...
  • 次世代センサーネットワークの実現に向けた化合物半導体化学センサの開発と高性能化に関する研究
    小澤・吉川記念エレクトロニクス研究助成基金:小澤・吉川記念エレクトロニクス研究助成基金
    研究期間 : 2008年 -2009年 
    代表者 : 佐藤 威友
  • 文部科学省:科学研究費補助金(若手研究(B))
    研究期間 : 2007年 -2008年 
    代表者 : 佐藤 威友
     
    電解液と半導体界面の電気化学反応により形成される多孔質(ポーラス)構造を利用し、少ない電子を局所的に閉じ込めて制御する「3次元量子ナノネットワーク」の基礎技術を確立した。本構造は、直径数100nm 深さ数μm の直線的な孔が配列した高密度ナノ構造が基盤となっており、非常に大きな表面積と優れた伝導特性および光学的特性を有し、高感度化学センサや高効率太陽光発電素子の基本構造として有望性を示す一連の研究成果を得た。
  • 文部科学省:科学研究費補助金(特定領域研究)
    研究期間 : 2007年 -2008年 
    代表者 : 橋詰 保, 金子 昌充, 佐藤 威友
     
    発光素子の効率・安定動作・信頼性には、バルクの結晶欠陥とともに、ヘテロ界面での禁制帯内連続電子準位(界面準位)や端面での表面準位の特性が影響する場合が多いが、これらの特性は明らかになっていない。本研究では、GaNおよびAlGaNのバルク欠陥準位と表面・端面・ヘテロ界面における表面電子準位を詳細に評価し、その特性の理解と制御を目的として研究を展開した。1) Al組成26%のAlGaN混晶にショットキー接合を形成し、暗中および光照射下での過渡容量応答評価を行なった。伝導帯下端より1.0eVおよび禁制帯中央付近の深い準位からの応答を検出し、詳しい解析の結果、5-8×10^<16>cm^<-3>程度の比較的高い密度を有することを明らかにした。2) 保護膜高温熱処理によるp-GaN表面の特性変化を詳細に評価した。XPS解析より1000℃以上の熱処理によりGa原子の外方拡散とMg原子の表面偏析が明らかになった。また、電流-電圧測定とPL評価より深い準位の生成による表面抵抗の増大が観測され、Ga空孔や格子間Mgに関連する複合欠陥の存在が示唆された。3) 電気化学酸化によるGaNおよびAlGaNの表面制御を検討した。酸化膜を溶液除去した表面に金属接合を形成した場合、接合特性の均一性が向上することが確認された。また、ドライエッチングで形成したナノ細線側面を選択的に酸化した場合、細線の伝導特性が...
  • High-efficiency energy-conversion devices based on semiconductor nanostructures
    研究期間 : 2008年
  • 選択的結晶成長による窒化ガリウム系ナノワイヤ・ネットワークの作製
    池谷科学技術振興財団:池谷科学技術振興財団研究助成金
    研究期間 : 2006年 -2007年 
    代表者 : 佐藤 威友
  • 化合物半導体ナノ構造の自己組織化形成と高感度化学センサへの応用
    村田学術振興財団:村田学術振興財団研究助成
    研究期間 : 2006年 -2007年 
    代表者 : 佐藤 威友
  • 文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 2005年 -2006年 
    代表者 : 橋詰 保, 葛西 誠也, 佐藤 威人友, 金子 昌充
     
    GaNおよびAlGaN混晶の表面結晶欠陥および不純物の振舞いを詳細に評価し、金属界面特性・絶縁体界面特性との相関、および、デバイスの電流崩壊、漏れ電流および劣化・破壊現象との関連性を系統的に調べてこれらの機構を明らかにし、表面欠陥制御・界面制御に基づきデバイスの信頼性・安定性の向上に直結する知見を得ることを目的とした。1)Al<0.26>Ga_<0.74>N混晶にショットキー接合を形成し、過渡容量応答解析を行ない、深い準位を評価した。秒オーダーの時間領域で解析することにより、伝導帯下端より0.9eVの位置に電子捕獲準位が1x10^<16>cm^<-3>程度の高密度で存在することを明らかにした。2)CN_x/SiN_x複合膜構造を利用した拡散プロセスを開発し、GaNへの炭素ドーピングを行なった。N_2雰囲気中で1000℃程度の熱処理を行なうことにより、炭素がGaN中へ拡散することを確認し、拡散した炭素は主として深い準位として振る舞うことを明らかにした。3)窒素ラジカル処理、超薄Al膜堆積、真空アニールにより、AlGaN表面近傍の窒素空孔欠陥と酸素不純物を低減する表面制御プロセスを開発し、Ni/AlGaNショットキー接合において、逆方向漏れ電流の大幅な低減と電流-電圧特性の明確な温度依存性を実現した。4)GaNおよびAlGaNとの絶縁膜界面を種々のプロセスにより形成し、高温および...
  • 文部科学省:科学研究費補助金(萌芽研究)
    研究期間 : 2005年 -2005年 
    代表者 : 長谷川 英機, 葛西 誠也, 佐藤 威友, 賈 鋭
     
    テラヘルツ(THz)帯の周波数領域では、効率よく電磁波を発生・増幅・検波する技術が確立されておらず「テラヘルツギャップ」とよばれている。本研究の目的は、ミリ波・テラヘルツ帯におい.て増幅・検波機能を果たす新しい進行波型半導体デバイスの可能性を、理論的および実験的に検討することにある。その原理は、半導体の2次元電子ガス中に発生するドリフトプラズマ波と、遅波構造による電磁波の空間高調波との相互作用を利用することにある。(1)電子の慣性項を取り入れたより厳密なプラズマ方程式をもとに、TMモード解析とグリーン関数を含むFredholm積分方程式による空間高調波解析を行い、その結果ミリ波・THz帯で、大きな負性コンダクタンスが得られことを確認した。そして、その機構が高周波では1サイクルあたりの衝突頻度が飛躍的に減ることにあることを示した。(2)さらに、解析を半導体の表面準位の効果を含むものに拡張し、表面状態による電界分布の変化やスクリーニングが、デバイスに悪影響を及ぼすことを見出した。(3)AlGaAs/GaAsヘテロ接合上に、インターディジタル型遅波構造を形成したデバイスについて、マイクロ・ミリ波帯で予備実験を行い、おおきなコンダクタンス変調を観測するとともに、理論解析と実験がよく一致することを実証した。これらは、Jpn.J.Appl.Physの正規論文やISDRS(Dec.2005...
  • 文部科学省:科学研究費補助金(若手研究(B))
    研究期間 : 2004年 -2005年 
    代表者 : 佐藤 威友
     
    本研究の目的は、化合物半導体低損傷プロセスによる高密度量子ナノ集積構造の形成手法と、その表面および界面のナノスケール制御手法を開発し、量子集積回路実現のための基礎技術を確立することである。平成17年度の研究成果は以下のようにまとめられる。1.分子線エピタキシャル成長法(MBE)により、ガリウム砒素(GaAs)(111)B加工基板上へGaAs/AlGaAs量子細線構造の選択的成長を行い、その形成メカニズム/サイズ制御性について調べた。成長温度、材料組成を系統的に変えて行なった一連の実験結果と、吸着原子の拡散方程式に基づく成長シミュレーションの結果から、加工基板が持つ結晶面方位の違いや材料原子の種類により、表面吸着原子の拡散/取り込まれ寿命が異なり、その表面拡散論的な成長機構により、GaAs細線の断面形状が説明されることがわかった。これらの結果を基礎とし、GaAs細線の位置とサイズを数nmオーダーの精度で制御することを可能にした。また、シミュレーションにより得られた成長条件を使って、断面が1辺40nmの三角形となるGaAs細線を実験的に作製することにも成功した。2.上で開発した成長シミュレーションプログラムを、窒化ガリウム(GaN)(0001)加工基板上への選択成長に適用した。Ga原子とAl原子に対して適切な拡散係数と表面取込み寿命を設定することにより、材料組成、結晶面方位など成...
  • 文部科学省:科学研究費補助金(基盤研究(A))
    研究期間 : 2003年 -2005年 
    代表者 : 本久 順一, プリミーラ モハン, 佐野 栄一, 福井 孝志, 佐藤 威友, 楊 林
     
    本研究では、有機金属気相成長(MOVPE)選択成長法によりフォトニック結晶(PhC)を作製する手法を確立し、またその特性評価および素子応用を目的として研究を行い、以下のような成果が得られた。まず、GaAs(111)BあるいはInP(111)B基板上に6角形の絶縁膜マスクを周期的に形成した基板に対して選択成長を行うことにより、GaAs系あるいはInP系材料による空気ロッド周期配列型2次元PhCをそれぞれ作製した。GaAs系PhCに対しては、AlGaAs犠牲層上に選択成長を行い、その後、選択ウェットエッチングにより犠牲層を除去することにより、エアーブリッジ構造の作製に成功すると共に、線欠陥・点欠陥を導入した構造の作製にも成功した。また、GaAs/AlGaAs量子井戸構造を有するPhCを作製し、量子井戸層からの発光を確認した。一方、InP系PhCに対しては、成長条件の最適化により、InGaAsおよびInPによる、周期400〜500nmの均一な空気ロッドアレイの作製に成功すると共に、ヘテロ構造やInP/InGaAs量子井戸の作製に成功した。特に、作製された量子井戸からの発光を確認し、光通信波長帯におけるPhCを利用した発光素子の作製の見通しを得た。また、GaAs(111)BあるいはInP(111)A基板に対して、6角形あるいは円形の開口を有するマスク基板を作製し、その後、MOVPE選...
  • 選択的半導体結晶成長法による量子集積回路作製プロセスの研究開発
    ノーステック財団:ノーステック財団基盤的研究開発育成事業(若手研究補助金)
    研究期間 : 2003年 -2004年 
    代表者 : 佐藤 威友
  • 文部科学省:科学研究費補助金(若手研究(B))
    研究期間 : 2002年 -2003年 
    代表者 : 佐藤 威友
     
    本研究課題では、微細ゲート電極形成技術および量子集積構造作製技術といった、量子集積回路の実現に向けた量子集積プロセスの開発を目的としている。平成15年度の研究成果は、以下のようにまとめられる。1.MBE選択成長法を用いて、量子集積回路の基本構造として有望なヘキサゴナル量子ナノ細線ネットワーク構造の作製に成功した。GaAs(001)加工基板上にMBE選択成長法により、<-110>方向-<510>方向の細線からなるヘキサゴナルGaAs/AlGaAsリッジ細線ネットワークの作製に成功した。細線の位置およびサイズは、成長条件と初期加工基板の設計により精密に制御可能である。また、構造および光学的特性の評価から、1mm四方以上(ヘキサゴナルノードで約1x10^7個分の領域)の広範囲にわたり、エネルギー半値幅20meVの均一な量子閉じこめ構造が形成されていることを確認した。同様に、GaAs(111)B加工基板を用いて、三回対称性を利用したヘキサゴナル細線ネットワークを形成することにも成功した。達成したヘキサゴナルノードの密度は、約10^9cm^<-2>であり、量子デバイスの高密度化に非常に有望な結果を得た。2.MBE選択成長法により作製した量子ナノ構造をベースに、量子細線トランジスタ・二分岐スイッチングデバイスの作製に成功した(論文投稿中)。(001)GaAs加工基板上にMBE選択成長法に...
  • 文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 2000年 -2002年 
    代表者 : 本久 順一, 韓 哲九, 安 海岩, 藤倉 序章, 佐藤 威友, 橋詰 保
     
    有機金属気相成長(MOVPE)法を用いた選択成長法により、フォトニック結晶(PC)を作製する技術の確立、およびその応用を目標として以下のような研究を行った。まず、SiO_2絶縁膜を堆積したGaAs(111)B基板上に対して、周期0.5μm程度の3角格子状に、円形あるいは6角形のマスク開口部を作製した基板を準備した後、GaAsおよびAlGaAsのMOVPE選択成長を行った。成長条件を最適化することにより、(111)B面に対して垂直な、{110}側面ファセットにより構成される、高アスペクト比6角柱による、2次元PCに応用可能な高均一周期構造作製に成功した。また、同様のマスクパターンを有するInP(111)Bマスク基板に対してMOVPE選択成長を行うことにより、InGaAs6角柱構造アレイを作製した。そのフォトルミネセンス特性の結果から、高品質の構造が作製されていことが確認され、InPをペースとしたPC作製の糸口が与えられた。また、6角形のSiO_2マスクを、3角格子状に周期的に配列させたGaAs(111)Bパターン基板に対して、GaAsの選択成長を行った。成長条件や、原料ガス供給のシーケンスを工夫することにより、マスク上への横方向成長を十分抑制した結果、6角形空気孔によるGaAsPCの作製に成功した。さらに、このPCを、AlGaAs(111)B表面上に形成した後、下部AlGaAs...
  • 電気化学プロセスによる金属-化合物半導体界面の制御とその電子デバイスへの応用
    日本学術振興会:科学研究費助成事業 特別研究員奨励費
    研究期間 : 1998年 -2000年 
    代表者 : 佐藤 威友
  • Self-assembled formation of semiconductor nanostructures using electrochemcial process and its application to sensors
    研究期間 : 1997年

教育活動情報

主要な担当授業

  • 先端デバイス学特論
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 情報科学研究科
    キーワード : 半導体材料、電子物性、電界効果トランジスタ、バイポーラトランジスタ、センサ、デジタルとアナログ、信号変換、離散化、量子化
  • 応用デバイス回路学特論
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 情報科学院
    キーワード : 半導体材料、電子物性、電界効果トランジスタ、バイポーラトランジスタ、センサ、デジタルとアナログ、信号変換、離散化、量子化
  • 先端デバイス学特論
    開講年度 : 2021年
    課程区分 : 博士後期課程
    開講学部 : 情報科学研究科
    キーワード : 半導体材料、電子物性、電界効果トランジスタ、バイポーラトランジスタ、センサ、デジタルとアナログ、信号変換、離散化、量子化
  • 応用デバイス回路学特論
    開講年度 : 2021年
    課程区分 : 博士後期課程
    開講学部 : 情報科学院
    キーワード : 半導体材料、電子物性、電界効果トランジスタ、バイポーラトランジスタ、センサ、デジタルとアナログ、信号変換、離散化、量子化
  • 応用数学Ⅰ
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : ベクトル空間,線形写像,固有値,勾配,発散,回転,ストークスの定理

大学運営

委員歴

  • 2021年04月 - 現在   電子情報通信学会 エレクトロニクスソサエティ 電子デバイス (ED) 研究会   電子デバイス (ED) 研究会専門委員会
  • 2021年 - 現在   Topical Workshop on Heterostructure Microelectronics (TWHM) 2022   実行委員
  • 2020年04月 - 現在   応用物理学会   APEX/JJAP編集委員
  • 2018年04月 - 現在   電子情報通信学会北海道支部   学生会顧問
  • 2016年 - 現在   応用物理学会   13.7 化合物及びパワーデバイス・プロセス技術・評価 世話人
  • 2020年 - 2021年   Solid State Devices and Materials (SSDM) 2021   実行委員
  • 2016年 - 2021年   GaN研究コンソーシアム   知的財産委員会 委員
  • 2021年   2021年電気化学秋季大会   現地実行委員
  • 2018年04月 - 2020年03月   ISPlasma   Program Committee
  • 2015年   国際固体素子・材料コンファレンス(SSDM)   実行委員
  • 2014年 - 2014年   電気化学会2014年秋季大会   実行委員
  • 2014年   応用物理学会秋季学術講演会   実行委員
  • 2005年04月 - 2007年03月   応用物理学会北海道支部   庶務幹事

社会貢献活動

  • 公開講義(札幌南高等学校)
    期間 : 2018年10月18日
    役割 : 講師
    主催者・発行元 : 北海道大学・札幌南高等学校
  • 公開講義(札幌開成中等教育学校)
    期間 : 2018年08月08日
    役割 : 講師
    主催者・発行元 : 北海道大学・札幌開成中等教育学校


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