研究者データベース

石川 史太郎(イシカワ フミタロウ)
量子集積エレクトロニクス研究センター
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

  • 教授

学位

  • 博士(工学)(北海道大学)

科研費研究者番号

  • 60456994

ORCID ID

J-Global ID

研究キーワード

  • 分子線エピタキシー   化合物半導体   ナノワイヤ   結晶成長   ダイヤモンド   

研究分野

  • ナノテク・材料 / ナノ材料科学
  • 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
  • ナノテク・材料 / 結晶工学
  • ナノテク・材料 / 応用物性

職歴

  • 2022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 教授
  • 2018年05月 - 2022年03月 愛媛大学 地球深部ダイナミクス研究センター 准教授 (兼任)
  • 2013年04月 - 2022年03月 愛媛大学 大学院・理工学研究科 准教授
  • 2007年06月 - 2013年03月 大阪大学 大学院工学研究科 助教
  • 2004年04月 - 2007年05月 Paul Drude Institute for Solid State Electronics 研究員

学歴

  • 2001年04月 - 2004年03月   北海道大学工学研究科博士後期課程
  • 1999年04月 - 2001年03月   北海道大学工学研究科博士前期課程
  • 1995年04月 - 1999年03月   北海道大学工学部

所属学協会

  • 日本結晶成長学会   IEEE   日本高圧力学会   日本表面真空学会   応用物理学会   日本金属学会   

研究活動情報

論文

  • Mattias Jansson, Fumitaro Ishikawa, Weimin M. Chen, Irina A. Buyanova
    ACS Nano 16 8 12666 - 12676 2022年08月23日
  • Takeru Tanigawa, Rikuo Tsutsumi, Fumitaro Ishikawa
    Japanese Journal of Applied Physics 61 SD SD1005 - SD1005 2022年06月01日 
    Abstract We obtain white luminescence by the oxidation of GaAs/Al-rich Al0.87Ga0.13As nanowire which is visible to the eye. The oxidized amorphous AlGaOx shell emits light over a wide spectral range covering entire visible wavelengths between 400–700 nm. The emission intensity depends on the oxidation temperature and time. Through the optimization of those conditions, we observe clear white light from the sample by the eye under the illumination of ultraviolet light-emitting diodes, which would be applicable as a white light phosphor.
  • Yoriko Tominaga, Yukihiro Horita, Yuto Takagaki, Fumitaka Nishiyama, Mitsuki Yukimune, Fumitaro Ishikawa
    Applied Physics Express 15 4 045504 - 045504 2022年04月01日 
    Abstract This study revealed the crystalline quality of the dilute bismide alloy GaAs1−xBix grown on a GaAs(001) substrate below 250 °C using molecular beam epitaxy. The substrate temperature and As flux played a dominant role in tuning the crystal structure between amorphous and single crystalline GaAs1−xBix, as well as in the Bi introduction in GaAs below 250 °C. Sample characterization demonstrated a substrate temperature of 250 °C produced single crystalline ∼200 nm thick GaAs0.982Bi0.018 with clear X-ray diffraction fringes, while the lower substrate temperature of 180 °C yielded an amorphous film. Rutherford backscattering spectrometry showed sufficient As supply at the growing surface provides uniform Bi distribution.
  • Masahiro Okujima, Kohei Yoshikawa, Shota Mori, Mitsuki Yukimune, Robert D. Richards, Bin Zhang, Weimin M. Chen, Irina A. Buyanova, Fumitaro Ishikawa
    Applied Physics Express 14 11 115002 - 115002 2021年11月01日 [査読有り]
  • Bin Zhang, Jan E. Stehr, Ping‐Ping Chen, Xingjun Wang, Fumitaro Ishikawa, Weimin M. Chen, Irina A. Buyanova
    Advanced Functional Materials 31 36 2104671 - 2104671 2021年09月
  • Iori Morita, Fumitaro Ishikawa, Anna Honda, Daiki Sato, Atsushi Koizumi, Tomohiro Nishitani, Masao Tabuchi
    Japanese Journal of Applied Physics 60 SB SBBK02 - SBBK02 2021年05月01日 [査読有り]
  • Rei Fukuta, Yohei Murakami, Hiroaki Ohfuji, Toru Shinmei, Tetsuo Irifune, Fumitaro Ishikawa
    Japanese Journal of Applied Physics 60 3 035501 - 035501 2021年03月01日 [査読有り][通常論文]
     
    We investigate the activation of Sn-V centers in diamond through ions implantation and the subsequent high pressure and high temperature (HPHT) treatment at 15 GPa and 2300 °C. Sn ions is implanted at fluences greater than 2 × 10 cm by varying the acceleration voltage up to 180 kV, which results in a Sn distribution with a uniform concentration of 1 × 10 cm down to a depth of 50 nm from the surface. The subsequent HPHT treatment recovers the transparent appearance and preserves the introduced Sn ions. The sample shows emission peaks composed of four levels that originate from the Sn-V centers. The two distinct emission peaks from the lower excited states to the split ground states are stable up to 77 K. At 10 K, these peaks are clearly observable at excitation powers spanning two orders of magnitude, which suggests the preferential carrier capture at these centers. 14 −2 20 −3
  • M Yukimune, R Fujiwara, T Mita, F Ishikawa
    Nanotechnology 31 50 505608 - 505608 2020年12月11日 [査読有り][通常論文]
  • Bin Zhang, Mattias Jansson, Yumiko Shimizu, Weimin M. Chen, Fumitaro Ishikawa, Irina A. Buyanova
    Nanoscale 12 40 20849 - 20858 2020年10月08日 [査読有り][通常論文]
     

    The formation of self-assembled nanodisks open up new avenue for designing novel quantum structures by utilizing a dilute bismide.

  • Teruyoshi Matsuda, Kyohei Takada, Kohsuke Yano, Satoshi Shimomura, Yumiko Shimizu, Fumitaro Ishikawa
    Applied Physics Letters 117 11 113105 - 113105 2020年09月14日 [査読有り][通常論文]
     
    © 2020 Author(s). We investigated microstructural deformations and Bi segregation in GaAs/GaAsBi/GaAs core-multishell heterostructures, which were triggered by the existence of twin defects. We observed Bi segregation at the interface of the twin defect interface in the GaAsBi shell. The phenomenon produced a horizontally spread Bi-accumulated nanostructure in the nanowire, which is probably induced by the large lattice mismatch between GaAs and GaAsBi. Bi is expected to penetrate through the twin defect interface, which results in the existence of Bi along twin defects and also inside the GaAs core. The existence of twin defects induced structural deformations and resulted in the formation of corrugated complex sidewall surfaces on the nanowire.
  • Rei Fukuta, Naoya Yamamoto, Yohei Murakami, Fumitaro Ishikawa, Hiroaki Ohfuji, Toru Shinmei, Tetsuo Irifune
    Materials Transactions 61 9 1707 - 1710 2020年09月01日 [査読有り][通常論文]
     
    © 2020 The Japan Institute of Metals and Materials. We disperse InP nanocrystals into nano-polycrystalline diamond during the direct conversion from graphite as a possible technique to control its solid-state properties. We synthesize diamond, using the high-pressure, high-temperature technique, which encapsulates an InP alloy in close contact with the graphite starting material. X-ray diffraction of the synthesized sample suggests the formation of polycrystalline diamond where the mixed crystals contain InP. Cross-sectional transmission electron microscopy shows the existence of InP nanocrystals with sizes up to approximately 100 nm. The existence of the InP elements can promote the formation of larger crystalline diamond grains arising from liquid sintering, which show a larger grain size over 400nm compared with the regions without InP, where a grain size of approximately 50 nm is observed.
  • Rikuo Tsutsumi, Naoki Tsuda, Bin Zhang, Weimin M. Chen, Irina A. Buyanova, Fumitaro Ishikawa
    Applied Physics Express 13 075003-1 - 4 2020年06月 [査読有り][通常論文]
  • Roman M. Balagula, Mattias Jansson, Mitsuki Yukimune, Jan E. Stehr, Fumitaro Ishikawa, Weimin M. Chen, Irina A. Buyanova
    Scientific Reports 10 8216-1 - 9 2020年05月 [査読有り][通常論文]
  • Coherent strain evolution at the initial growth stage of AlN on SiC(0001) proved by in situ synchrotron X-ray diffraction
    Hidetoshi Suzuki, Fumitaro Ishikawa, Takuo Sasaki, Masamitu Takahasi
    Applied Physics Express 13 055501-1 - 055501-5 2020年04月 [査読有り][通常論文]
  • Deep-ultraviolet near band-edge emissions from nano-polycrystalline diamond
    Ryota Ishii, Rei Fukuta, Fumitaro Ishikawa, Masafumi Matsushita, Hiroaki Ohfuji, Toru Shinmei, Tetsuo Irifune, Mitsuru Funato, Yoichi Kawakami
    High Pressure Research 40 1 140 - 147 2020年02月 [査読有り][通常論文]
  • Jan Eric Stehr, Roman Balagula, Mattias Jansson, Mitsuki Yukimune, Ryo Fujiwara, Fumitaro Ishikawa, Weimin Chen, Irina A Buyanova
    Nanotechnology 31 065702-1 - 6 {IOP} Publishing 2020年01月 [査読有り][通常論文]
  • Teruyoshi Matsuda, Kyohei Takada, Kosuke Yano, Rikuo Tsutsumi, Kohei Yoshikawa, Satoshi Shimomura, Yumiko Shimizu, Kazuki Nagashima, Takeshi Yanagida, Fumitaro Ishikawa
    Nano Letters 19 12 8510 - 8518 2019年12月 [査読有り][通常論文]
     
    We control the formation of Bi-induced nanostructures on the growth of GaAs/GaAsBi core-shell nanowires (NWs). Bi serves as not only a constituent but also a surfactant and nanowire growth catalyst. Thus, we paved a way to achieve unexplored III-V nanostructures employing the characteristic supersaturation of catalyst droplets, structural modifications induced by strain, and incorporation into the host GaAs matrix correlated with crystalline defects and orientations. When Ga is deficient during growth, Bi accumulates on the vertex of core GaAs NWs and serves as a nanowire growth catalyst for the branched structures to azimuthal < 112 >. We find a strong correlation between Bi accumulation and stacking faults. Furthermore, Bi is preferentially incorporated on the GaAs (112)B surface, leading to spatially selective Bi incorporation into a confined area that has a Bi concentration of over 7%. The obtained GaAs/GaAsBi/GaAs heterostructure with an interface defined by the crystalline twin defects in a zinc-blende structure can be potentially applied to a quantum confined structure. Our finding provides a rational design concept for the creation of GaAsBi based nanostructures and the control of Bi incorporation beyond the fundamental limit.
  • 石川史太郎
    日本結晶成長学会誌 46 2 04-1 - 9 2019年07月 [査読有り][招待有り]
  • T. Matsuda, K. Takada, K. Yano, S. Shimomura, F. Ishikawa
    Journal of Applied Physics 125 194301-1 - 5 2019年05月 [査読有り][招待有り]
  • Mitsuki Yukimune, Ryo Fujiwara, Takaya Mita, Naoki Tsuda, Jun Natsui, Yumiko Shimizu, Mattias Jansson, Roman Balagula, W M Chen, Irina A Buyanova, Fumitaro Ishikawa
    Nanotechnology 30 244002  2019年02月 [査読有り][通常論文]
  • Shula Chen, Mitsuki Yukimune, Ryo Fujiwara, Fumitaro Ishikawa, Weimin M Chen, Irina A Buyanova
    Nano Letters 19 2 885 - 890 2019年01月 [査読有り][通常論文]
  • Fumitaro Ishikawa, Kotaro Higashi, Satoshi Fuyuno, Masato Morifuji, Masahiko Kondow, Achim Trampert
    Scientific Reports 8 1 5962-1 - 5962-13 2018年12月01日 [査読有り][通常論文]
     
    We study the effects of annealing on (Ga0.64,In0.36) (N0.045,As0.955) using hard X-ray photoelectron spectroscopy and X-ray absorption fine structure measurements. We observed surface oxidation and termination of the N-As bond defects caused by the annealing process. Specifically, we observed a characteristic chemical shift towards lower binding energies in the photoelectron spectra related to In. This phenomenon appears to be caused by the atomic arrangement, which produces increased In-N bond configurations within the matrix, as indicated by the X-ray absorption fine structure measurements. The reduction in the binding energies of group-III In, which occurs concomitantly with the atomic rearrangements of the matrix, causes the differences in the electronic properties of the system before and after annealing.
  • M. Jansson, F. Ishikawa, W. M. Chen, I. A. Buyanova
    Physical Review Applied 10 044040-1 - 12 2018年10月 [査読有り][通常論文]
  • Rei Fukuta, Naoya Yamamoto, Fumitaro Ishikawa, Masafumi Matsushita, Tsuyoshi Yoshitake, Hiroshi Ikenoue, Hiroaki Ohfuji, Toru Shinmei, Tetsuo Irifune
    Japanese Journal of Applied Physics 57 11 118004-1 - 118004-3 2018年10月 [査読有り][通常論文]
     
    We propose a simple and easy electrode formation technique on nanopolycrystalline diamond (NPD) synthesized by a high-temperature and high-pressure technique. The stronger light absorption nature of NPD than of standard transparent diamond enables the laser irradiation process on NPD. Pulsed laser irradiation using an ArF excimer laser under atmospheric condition drastically reduced the resistance of the NPD surface by forming graphite. Repetition of the laser irradiation reduced the resistance, showing a resistance of 300 Omega for the laser-irradiated area of 100 x 150 mu m(2). These results indicate the applicability of pulsed laser irradiation to an NPD apparatus having a conductive electrode, as well as electronic device processes. (C) 2018 The Japan Society of Applied Physics
  • Mitsuki Yukimune, Ryo Fujiwara, Hiroya Ikeda, Kohsuke Yano, Kyohei Takada, Mattias Jansson, Weimin Chen, Irina Buyanova, Fumitaro Ishikawa
    Applied Physics Letters 113 011901-1 - 5 2018年07月 [査読有り][通常論文]
  • Rei Fukuta, Fumitaro Ishikawa, Akihiro Ishikawa, Kohsuke Hamada, Masafumi Matsushita, Hiroaki Ohfuji, Toru Shinmei, Tetsuo Irifune
    Diamond and Related Materials 84 66 - 70 2018年04月01日 [査読有り][通常論文]
     
    We investigated inherent electronic properties of ultra-hard nano-polycrystalline diamond (NPD) synthesised at 15 GPa and 2300 °C. NPD exhibited a p-type semiconducting property with a resistivity of 1 × 106 and 4 × 102 Ω cm at 400 °C and 800 °C, respectively, with activation energies as high as 1.2 eV. The mobility was 2 cm2/Vs at 800 °C. The observed transport was considered to be attributed to grain boundary. Cathodoluminescence spectra show defect-related peaks with dominant peaks at 2.8 eV close to band-A and peaks below 2 eV, which is possibly related to crystal defects. In contrast, photoluminescence excited with a wavelength of 405 nm resonantly excited peaks having energies lower than 2.1 eV. The large density of crystalline defects such as grain boundaries and impurities in the NPD would result in the characteristic electronic and optical properties.
  • Pallavi Kisan Patil, Fumitaro Ishikawa, Satoshi Shimomura
    JOURNAL OF ALLOYS AND COMPOUNDS 725 694 - 699 2017年11月 [査読有り][通常論文]
     
    Eleven periods of GaAsBi/GaAs multiple quantum wells (MQWs) on (100) GaAs substrates were grown by molecular beam epitaxy (MBE) using the two-substrate-temperatures (TST) technique. In the TST technique, the substrate temperature was set at T-GaAsBi = 350 degrees C for GaAsBi layers and T-GaAs = 550 degrees C for GaAs layers for the growth of MQWs. The structural and optical characterization of GaAsBi/GaAs MQWs using TST technique was carried out for growth optimization by changing As-4/Ga beam equivalent pressure (BEP) ratio. Atomic force microscope observation shows high As-4/Ga BEP ratio supply can prevents roughening of the GaAsBi layer surface of MQWs. High resolution x-ray diffraction analysis results reveal Bi incorporation enhancement with increasing As-4/Ga BEP ratio. The reciprocal space mapping shows highly strained MQWs layers can be grown without relaxation with respect to the GaAs substrate at optimized growth conditions. At room temperature 1.22 mu m photoluminescence emission was obtained from GaAs0.962Bi0.038/GaAs MQWs grown using TST technique. (C) 2017 Elsevier B.V. All rights reserved.
  • Pallavi Kisan Patil, Fumitaro Ishikawa, Satoshi Shimomura
    SUPERLATTICES AND MICROSTRUCTURES 106 50 - 57 2017年06月 [査読有り][通常論文]
     
    Multi-quantum wells (MQWs) of GaAsBi/GaAs were grown by molecular beam epitaxy (MBE) and dependence of its surface morphology, Bi content and optical properties on Bi beam equivalent pressure (BEP) were studied. For the MQWs growth, two-substrate temperatures (TST) technique was used, where GaAsBi layers were grown at T-GaAsBi = 350 degrees C and GaAs layers at T-GAs = 550 degrees C. The segregated bismuth atoms were desorbed by increasing the substrate temperature from T-GaAsBi to T-GaAs after finishing the growth of each GaAsBi layer of MQWs including the topmost GaAsBi layer. The surface of the topmost GaAsBi layer shows no sign of Bi droplet formation even for the MQWs grown at highest Bi supply. The Bi content increases up to 3.8% in proportional to the Bi BEP and decreases in a higher Bi BEP region. (C) 2017 Elsevier Ltd. All rights reserved.
  • E. Luna, R. Gargallo-Caballero, F. Ishikawa, A. Trampert
    APPLIED PHYSICS LETTERS 110 20 201906-1 - 5 2017年05月 [査読有り][通常論文]
     
    The microstructure and the element distribution across tensile-strained nitrogen delta-doped GaAs/(Al, Ga) As quantum wells (QW) are investigated by transmission electron microscopy. We find that the nitrogen sub-monolayer insertion results in a several monolayer thick Ga(As, N) layer with thickness and lateral composition fluctuations. The thickness and composition fluctuations are not arbitrary, but they are anticorrelated, i.e., the Ga(As, N) layer is thinner in areas of higher nitrogen content and vice versa. Thus, regardless of the specific position along the QW, the amount of incorporated nitrogen remains constant and close to its nominal value. The increase in the nitrogen content at the insertion promotes an anisotropic shape transition towards highly faceted three-dimensional structures. Our experimental observations indicate that the two-dimensional to three-dimensional morphological transition is determined by intrinsic factors associated with the different Ga-N and Ga-As bonds and hence occurs regardless of the epitaxial strain state of the layers. Published by AIP Publishing.
  • Shula Chen, Mattias Jansson, Jan E. Stehr, Yuqing Huang, Fumitaro Ishikawa, Weimin M. Chen, Irina A. Buyanova
    NANO LETTERS 17 3 1775 - 1781 2017年03月 [査読有り][通常論文]
     
    Nanowire (NW) lasers operating in the near infrared spectral range are of significant technological importance for applications in telecommunications, sensing, and medical diagnostics. So far, lasing within this spectral range has been achieved using GaAs/AlGaAs, GaAs/GaAsP, and InGaAs/GaAs core/shell NWs. Another promising III-V material, not yet explored in its lasing capacity, is the dilute nitride GaNAs. In this work, we demonstrate, for the first time, optically pumped lasing from the GaNAs shell of a single GaAs/GaNAs core/shell NW. The characteristic "S"-shaped pump power dependence of the lasing intensity, with the concomitant line width narrowing, is observed, which yields a threshold gain, g(th), of 3300 cm(-1) and a spontaneous emission coupling factor beta, of 0.045. The dominant lasing peak is identified to arise from the HE21b, cavity mode, as determined from its pronounced emission polarization along the NW axis combined with theoretical calculations of lasing threshold for guided modes inside the nanowire. Even without intentional pas sivation of the NW surface, the lasing emission can be sustained up to 150 K. This is facilitated by the improved surface quality due to nitrogen incorporation, which partly suppresses the surface-related nonradiative recombination centers via nitridation. Our work therefore represents the first step toward development of room-temperature infrared NW lasers based on dilute nitrides with extended tunability in the lasing wavelength.
  • Pallavi Kisan Patil, Esperanza Luna, Teruyoshi Matsuda, Kohki Yamada, Keisuke Kamiya, Fumitaro Ishikawa, Satoshi Shimomura
    NANOTECHNOLOGY 28 10 105702  2017年03月 [査読有り][通常論文]
     
    We report a GaAs0.96Bi0.04/GaAs multiple quantum well (MQW) light emitting diode ( LED) grown by molecular beam epitaxy using a two-substrate-temperature (TST) technique. In particular, the QWs and the barriers in the intrinsic region were grown at the different temperatures of T-GaAsBi = 350 degrees C and T-GaAs = 550. degrees C, respectively. Investigations of the microstructure using transmission electron microscopy (TEM) reveal homogeneous MQWs free of extended defects. Furthermore, the local determination of the Bi distribution profile across the MQWs region using TEM techniques confirm the uniform Bi distribution, while revealing a slightly chemically graded GaAs-on-GaAsBi interface due to Bi surface segregation. Despite this small broadening, we found that Bi segregation is significantly reduced ( up to 18% reduction) compared to previous reports on Bi segregation in GaAsBi/GaAs MQWs. Hence, the TST procedure proves as a very efficient method to reduce Bi segregation and thus increase the quality of the layers and interfaces. These improvements positively reflect in the optical properties. Room temperature photoluminescence and electroluminescence (EL)at 1.23 mu m emission wavelength are successfully demonstrated using TST MQWs containing less Bi content than in previous reports. Finally, LED fabricated using the present TST technique show currentvoltage (I-V) curves with a forward voltage of 3.3 V at an injection current of 130 mA under 1.0 kA cm(-2) current excitation. These results not only demonstrate that TST technique provides optical device quality GaAsBi/GaAs MQWs but highlight the relevance of TST-based growth techniques on the fabrication of future heterostructure devices based on dilute bismides.
  • Kohei Nishioka, Hidetoshi Suzuki, Kentaro Sakai, Fumitaro Ishikawa
    PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 254 2 2017年02月 [査読有り][通常論文]
     
    We investigate material conversion of compound semiconductor GaAs nanowires to extend their functions. By heating the GaAs nanowires in indium melt, the indium was introduced into the GaAs nanowire, converting the nanowires to be InGaAs compounds. The further heating treatment in N-2 ambient progresses the diffusion of Si element from the substrate, eventually forming the indium-silicide compound nanowires. The results suggest the conversion technique possibly extend the functions of the nanowire system by the exchange, introduction, or integrations of various materials.
  • Wojciech M. Linhart, Szymon J. Zelewski, Fumitaro Ishikawa, Satoshi Shimomura, Robert Kudrawiec
    Novel Compound Semiconductor Nanowires: Materials, Devices, and Applications 161 - 176 2017年01月01日 
    This chapter provides an overview of the existing research on dilute III-V-Bi nanowires, particularly dilute GaAsBi nanowires. The development of dilute III-V bismides nanowires is in the first stages because the growth of these nanostructures is a major challenge to be overcome. So far, in the family of III-V-Bi nanowires, only dilute GaAsBi nanowires have been grown by molecular beam epitaxy or metalorganic vapor phase epitaxy. Here we present the recent progress in the growth and structural and optical properties of these structures. Additionally, we will show that photoacoustic spectroscopy is a powerful tool to study the energy gap of semiconductor nanowires.
  • Fumitaro Ishikawa, Pierre Corfdir, Uwe Jahn, Oliver Brandt
    ADVANCED OPTICAL MATERIALS 4 12 2017 - 2020 2016年12月 [査読有り][通常論文]
  • Pallavi Kisan Patil, Fumitaro Ishikawa, Satoshi Shimomura
    SUPERLATTICES AND MICROSTRUCTURES 100 1205 - 1212 2016年12月 [査読有り][通常論文]
     
    Eleven periods of GaAsBi/GaAs multiple quantum wells (MQWs) grown on (411)A and (411)B GaAs substrates at T-GaAsBi = 350 degrees C and T-GaAs = 550 degrees C by molecular beam epitaxy (MBE) and their structural and optical properties were investigated. The high resolution Xray diffraction (HRXRD) analysis shows increment in Bi composition with the increasing As-4 beam equivalent pressure (BEP). The reciprocal space mapping (RSM) reveals highly strained GaAsBi/GaAs MQWs layers can be grown without relaxation with respect to the (411) GaAs substrate on both A and B sides at an optimized growth condition of Bi and As4 BEP; while (411)A sample with higher bismuth content (5.5 %) shows lattice dislocation of MQWs due to lateral strain. The temperature-dependent photoluminescence (PL) shows 1.26 pm emission at room temperature from both the (411)A and (411)B samples for GaAs0.97Bi0.03/GaAs MQWs. It is perceived that GaAsBi/GaAs MQWS can be successfully grown on both sides of (411) GaAs substrate. (C) 2016 Elsevier Ltd. All rights reserved.
  • Fumitaro Ishikawa, Pierre Corfdir, Uwe Jahn, Oliver Brandt
    ADVANCED OPTICAL MATERIALS 4 12 2017 - 2020 2016年12月 [査読有り][通常論文]
  • J. E. Stehr, S. L. Chen, M. Jansson, F. Ishikawa, W. M. Chen, I. A. Buyanova
    APPLIED PHYSICS LETTERS 109 20 203103-1 - 5 2016年11月 [査読有り][通常論文]
     
    Photoluminescence and optically detected magnetic resonance (ODMR) spectroscopies are used to investigate the formation and role of defects in GaAs/GaNxAs1-x core/shell nanowires (NWs) grown by molecular beam epitaxy on Si substrates. Gallium vacancies, which act as non-radiative recombination (NRR) centers, are identified by ODMR. It is shown that the defects are formed in bulk regions, i.e., not on the surface, of the GaNAs shell and that their concentration increases with increasing nitrogen content. Temperature dependent photoluminescence experiments reveal, on the other hand, suppressed thermal quenching of the near-band-edge emission with increasing [N]. This leads to the conclusion that the dominant NRR processes in the studied NWs are governed by surface defects, whereas the role of gallium vacancies in the observed thermally activated NRR is minor. Published by AIP Publishing.
  • Szymon J. Zelewski, Jan Kopaczek, Wojciech M. Linhart, Fumitaro Ishikawa, Satoshi Shimomura, Robert Kudrawiec
    APPLIED PHYSICS LETTERS 109 18 182106-1 - 5 2016年10月 [査読有り][通常論文]
     
    GaAsBi/GaAs nanowires (NWs) grown on Si substrate and proper reference samples have been studied by photoacoustic (PA) spectroscopy. It has been shown that PA signal originating from NWs is quite strong and can be easily identified in the PA spectra, as well as distinguished from the signal originating from the Si substrate. The absorption edge of GaAsBi/GaAs and GaAs NWs has been determined from the analysis of amplitude PA spectra to be 1.26 eV and 1.42 eV, respectively. These values are consistent with the band gap reduction resulting from the introduction of similar to 2% Bi in bulk GaAsBi alloy. The presented results prove that, despite light scattering, which is typical for NWs, PA spectroscopy is an excellent tool to study the absorption edge in semiconductor NWs. Published by AIP Publishing.
  • S. Filippov, M. Jansson, J. E. Stehr, J. Palisaitis, P. O.A. Persson, F. Ishikawa, W. M. Chen, I. A. Buyanova
    Nanoscale 8 35 15939 - 15947 2016年09月21日 [査読有り][通常論文]
     
    Recent developments in fabrication techniques and extensive investigations of the physical properties of III-V semiconductor nanowires (NWs), such as GaAs NWs, have demonstrated their potential for a multitude of advanced electronic and photonics applications. Alloying of GaAs with nitrogen can further enhance the performance and extend the device functionality via intentional defects and heterostructure engineering in GaNAs and GaAs/GaNAs coaxial NWs. In this work, it is shown that incorporation of nitrogen in GaAs NWs leads to formation of three-dimensional confining potentials caused by short-range fluctuations in the nitrogen composition, which are superimposed on long-range alloy disorder. The resulting localized states exhibit a quantum-dot like electronic structure, forming optically active states in the GaNAs shell. By directly correlating the structural and optical properties of individual NWs, it is also shown that formation of the localized states is efficient in pure zinc-blende wires and is further facilitated by structural polymorphism. The light emission from these localized states is found to be spectrally narrow (∼50-130 μeV) and is highly polarized (up to 100%) with the preferable polarization direction orthogonal to the NW axis, suggesting a preferential orientation of the localization potential. These properties of self-assembled nano-emitters embedded in the GaNAs-based nanowire structures may be attractive for potential optoelectronic applications.
  • S. Filippov, M. Jansson, J. E. Stehr, J. Palisaitis, P. O. A. Persson, F. Ishikawa, W. M. Chen, I. A. Buyanova
    NANOSCALE 8 35 15939 - 15947 2016年09月 [査読有り][通常論文]
     
    Recent developments in fabrication techniques and extensive investigations of the physical properties of III-V semiconductor nanowires (NWs), such as GaAs NWs, have demonstrated their potential for a multitude of advanced electronic and photonics applications. Alloying of GaAs with nitrogen can further enhance the performance and extend the device functionality via intentional defects and heterostructure engineering in GaNAs and GaAs/GaNAs coaxial NWs. In this work, it is shown that incorporation of nitrogen in GaAs NWs leads to formation of three-dimensional confining potentials caused by short-range fluctuations in the nitrogen composition, which are superimposed on long-range alloy disorder. The resulting localized states exhibit a quantum-dot like electronic structure, forming optically active states in the GaNAs shell. By directly correlating the structural and optical properties of individual NWs, it is also shown that formation of the localized states is efficient in pure zinc-blende wires and is further facilitated by structural polymorphism. The light emission from these localized states is found to be spectrally narrow (similar to 50-130 mu eV) and is highly polarized (up to 100%) with the preferable polarization direction orthogonal to the NW axis, suggesting a preferential orientation of the localization potential. These properties of self-assembled nano-emitters embedded in the GaNAs-based nanowire structures may be attractive for potential optoelectronic applications.
  • Shula Chen, Mattias Jansson, Stanislav Filippov, Fumitaro Ishikawa, Weimin M. Chen, Irina A. Buyanova
    Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics 34 4 2016年07月01日 [査読有り][通常論文]
     
    Comprehensive studies of GaAs/GaNAs coaxial nanowires grown on Si substrates are carried out by temperature-dependent photoluminescence (PL) and PL excitation, to evaluate effects of the shell formation on carrier recombination. The PL emission from the GaAs core is found to transform into a series of sharp PL lines upon radial growth of the GaNAs shell, pointing toward the formation of localization potentials in the core. This hampers carrier transfer at low temperatures from the core in spite of its wider bandgap. Carrier injection from the core to the optically active shell is found to become thermally activated at T > 60 K, which implies that the localization potentials are rather shallow.
  • Shula Chen, Mattias Jansson, Stanislav Filippov, Fumitaro Ishikawa, Weimin M. Chen, Irina A. Buyanova
    Journal of Vacuum Science & Technology B 34 4 04J104  2016年07月 [査読有り][通常論文]
     
    Comprehensive studies of GaAs/GaNAs coaxial nanowires grown on Si substrates are carried out by temperature-dependent photoluminescence (PL) and PL excitation, to evaluate effects of the shell formation on carrier recombination. The PL emission from the GaAs core is found to transform into a series of sharp PL lines upon radial growth of the GaNAs shell, pointing toward the formation of localization potentials in the core. This hampers carrier transfer at low temperatures from the core in spite of its wider bandgap. Carrier injection from the core to the optically active shell is found to become thermally activated at T>60 K, which implies that the localization potentials are rather shallow. (C) 2016 American Vacuum Society.
  • Takuo Sasaki, Fumitaro Ishikawa, Tomohiro Yamaguchi, Masamitu Takahasi
    JAPANESE JOURNAL OF APPLIED PHYSICS 55 5 05FB05  2016年05月 [査読有り][通常論文]
     
    A molecular beam epitaxy (MBE) chamber dedicated to nitride growth was developed at the synchrotron radiation facility SPring-8. This chamber has two beryllium windows for incident and outgoing X-rays, and is directly connected to an X-ray diffractometer, enabling in situ synchrotron X-ray measurements during the nitride growth. Experimental results on initial growth dynamics in GaN/SiC, AlN/SiC, and InN/GaN heteroepitaxy were presented. We achieved high-speed and high-sensitivity reciprocal space mapping with a thickness resolution of atomic-layer scale. This in situ measurement using the high-brilliance synchrotron light source will be useful for evaluating structural variations in the initial growth stage of nitride semiconductors. (C) 2016 The Japan Society of Applied Physics
  • Masato Morifuji, Fumitaro Ishikawa
    PHYSICA B-CONDENSED MATTER 485 89 - 93 2016年03月 [査読有り][通常論文]
     
    Contrary to the conventional empirical law, band gap of the dilute nitride semiconductors decreases with increasing nitrogen concentration. In spite of a number of investigations, the origin of this "large band gap bowing" is still under debate. In order to elucidate this phenomenon, we investigate change of the band edge energy of GaNxAs1-x due to nitrogen by using the perturbation theory. We found that energy shift of the conduction band edge is arising from intervalley mixing between the Gamma- and L-states and/or Gamma- and X-states mainly induced by displacement of Ga atoms around nitrogen. The valence band edge state shows upward shift in spite of negative potential of nitrogen. These results are well understood from symmetry of the wavefunctions and the perturbation potential. (C) 2016 Elsevier B.V. All rights reserved.
  • S. Filippov, F. Ishikawa, W. M. Chen, I. A. Buyanova
    SEMICONDUCTOR SCIENCE AND TECHNOLOGY 31 2 025002  2016年02月 [査読有り][通常論文]
     
    GaNAs-based nanowires (NWs) form a novel material system of potential importance for applications in advanced optoelectronic and photonic devices, thanks to the advantages provided by band-structure engineering, one-dimensional architecture and the possibility to combine them with mainstream silicon technology. In this work we utilize the micro-Raman scattering technique to systematically study the structural properties of such GaAs/GaNAs core/shell NW structures grown by molecular beam epitaxy on a Si substrate. It is shown that the employed one-dimensional architecture allows the fabrication of a GaNAs shell with a low degree of alloy disorder and weak residual strain, at least within the studied range of nitrogen (N) compositions [N] < 0.6%. Raman scattering by the GaAs-like and GaN-like phonons is found to be enhanced when the excitation energy approaches the E+ transition energy. Since this effect is found to be more pronounced for the GaN-like phonons, the involved intermediate states are concluded to be localized in proximity to N impurities, i.e. they likely represent N-related cluster states located in proximity to E+.
  • Pallavi Patil, Fumitaro Ishikawa, Satoshi Shimomura
    CS MANTECH 2016 - International Conference on Compound Semiconductor Manufacturing Technology 341 - 344 2016年 
    We have grown GaAsBi/GaAs MQWs on GaAs (411)A and (411)B substrates by MBE and investigated arsenic pressure dependence of the Bi concentration of GaAsBi layers and optical characteristics of MQWs. The highest bismuth composition (x = 0.03) was obtained for GaAsBi layers grown under a arsenic pressure of 1.0×10-5 mbar for both (411)A and (411)B MQWs. The MQWs grown on both substrates at the optimized arsenic pressure show a PL peak at 1.26 μm. The MQWs on (411)A and (411)B substrate showed 3 times and 2 times stronger integrated RT PL intensity, respectively, than simultaneously grown (100) MQWs.
  • I. A. Buyanova, W. M. Chen, F. Ishikawa, C. W. Tu
    2016 IEEE 16TH INTERNATIONAL CONFERENCE ON NANOTECHNOLOGY (IEEE-NANO) 38 - 41 2016年 [査読有り][通常論文]
     
    In this paper we review our recent results on optical properties of coaxial nanowires (NWs) based on dilute nitride alloys, such as GaAsN and GaNP. We show that these structures have a high structural and optical quality, and can potentially be used as polarized nano-scale light sources that emit linearly polarized light with the polarization direction perpendicular to the wire axis even in zincblende NWs of various diameters. We also demonstrate that, though the GaNxP1-x alloys have rather wide bandgap energies of 1.9 - 2.3 eV, the coaxial GaNP NWs absorb infrared light via two-step two-photon absorption.
  • Mattias Jansson, Weimin M. Chen, Irina A. Buyanova, Fumitaro Ishikawa
    2016 IEEE 16TH INTERNATIONAL CONFERENCE ON NANOTECHNOLOGY (IEEE-NANO) 42 - 44 2016年 [査読有り][通常論文]
     
    this work we investigate properties of ultra-narrow photoluminescence lines originating from recombination of excitons trapped by short-range potential fluctuations, caused by alloy disorder in GaAs/GaNAs core/shell nanowires. From power-dependent photoluminescence measurements we show that the emission behavior is consistent with biexciton-exciton cascade recombination in quantum dots. We also show that the thermal activation energy from the related localized states is of the order of 9-30 meV, suggesting a rather shallow confinement potential.
  • Kohei Nishioka, Hidetoshi Suzuki, Kentaro Sakai, Fumitaro Ishikawa
    2016 COMPOUND SEMICONDUCTOR WEEK (CSW) INCLUDES 28TH INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE & RELATED MATERIALS (IPRM) & 43RD INTERNATIONAL SYMPOSIUM ON COMPOUND SEMICONDUCTORS (ISCS) 2016年 [査読有り][通常論文]
  • Pallavi Patil, Fumitaro Ishikawa, Satoshi Shimomura
    2016 COMPOUND SEMICONDUCTOR WEEK (CSW) INCLUDES 28TH INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE & RELATED MATERIALS (IPRM) & 43RD INTERNATIONAL SYMPOSIUM ON COMPOUND SEMICONDUCTORS (ISCS) 2016年 [査読有り][通常論文]
  • Kyohei Takada, Yuto Kubota, Yoshihiko Akamatsu, Pallavi Patil, Fumitaro Ishikawa, Satoshi Shimomura
    2016 COMPOUND SEMICONDUCTOR WEEK (CSW) INCLUDES 28TH INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE & RELATED MATERIALS (IPRM) & 43RD INTERNATIONAL SYMPOSIUM ON COMPOUND SEMICONDUCTORS (ISCS) 2016年 [査読有り][通常論文]
  • Takuo Sasaki, Fumitaro Ishikawa, Masamitu Takahasi
    APPLIED PHYSICS LETTERS 108 1 012102  2016年01月 [査読有り][通常論文]
     
    We report an anomalous lattice deformation of GaN layers grown on SiC(0001) by molecular beam epitaxy. The evolution of the lattice parameters during the growth of the GaN layers was measured by in situ synchrotron X-ray diffraction. The lattice parameters in the directions parallel and normal to the surface showed significant deviation from the elastic strains expected for lattice-mismatched films on substrates up to a thickness of 10 nm. The observed lattice deformation was well explained by the incorporation of hydrostatic strains due to point defects. The results indicate that the control of point defects in the initial stage of growth is important for fabricating GaN-based optoelectronic devices. (C) 2016 AIP Publishing LLC.
  • F. Ishikawa
    QUANTUM SENSING AND NANO ELECTRONICS AND PHOTONICS XIII 9755 975526  2016年 [査読有り][招待有り]
     
    GaAs related compound semiconductor heterostructures are one of the most developed materials for photonics. Those have realized various photonic devices with high efficiency, e.g., lasers, electro-optical modulators, and solar cells. To extend the functions of the materials system, diluted nitride and bismide has been paid attention over the past decade. They can largely decrease the band gap of the alloys, providing the greater tunability of band gap and strain status, eventually suppressing the non-radiative Auger recombinations. On the other hand, selective oxidation for AlGaAs is a vital technique for vertical surface emitting lasers. That enables precisely controlled oxides in the system, enabling the optical and electrical confinement, heat transfer, and mechanical robustness. We introduce the above functions into GaAs nanowires. GaAs/GaAsN core-shell nanowires showed clear redshift of the emitting wavelength toward infrared regime. Further, the introduction of N elongated the carrier lifetime at room temperature indicating the passivation of non-radiative surface recombinations. GaAs/GaAsBi nanowire shows the redshift with metamorphic surface morphology. Selective and whole oxidations of GaAs/AlGaAs core-shell nanowires produce semiconductor/oxide composite GaAs/AlGaOx and oxide GaOx/AlGaOx core-shell nanowires, respectively. Possibly sourced from nano-particle species, the oxide shell shows white luminescence. Those property should extend the functions of the nanowires for their application to photonics.
  • Fumitaro Ishikawa, Yoshihiko Akamatsu, Kentaro Watanabe, Fumihiko Uesugi, Shunsuke Asahina, Uwe Jahn, Satoshi Shimomura
    NANO LETTERS 15 11 7265 - 7272 2015年11月 [査読有り][通常論文]
     
    GaAs/GaAsBi coaxial multishell nanowires were grown by molecular beam epitaxy. Introducing Bi results in a characteristic nanowire surface morphology with strong roughening. Elemental mappings clearly show the formation of the GaAsBi shell with inhomogeneous Bi distributions within the layer surrounded by the outermost GaAs, having a strong structural disorder at the wire surface. The nanowire exhibits a predominantly ZB structure from the bottom to the middle part. The polytipic WZ structure creates denser twin defects in the upper part than in the bottom and middle parts of the nanowire. We observe room temperature cathodoluminescence from the GaAsBi nanowires with a broad spectral line shape between 1.1 and 1.5 eV, accompanied by multiple peaks. A distinct energy peak at 1.24 eV agrees well with the energy of the reduced GaAsBi alloy band gap by the introduction of 2% Bi. The existence of localized states energetically and spatially dispersed throughout the NW are indicated from the low temperature cathodoluminescence spectra and images, resulting in the observed luminescence spectra characterized by large line widths at low temperatures as well as by the appearance of multiple peaks at high temperatures and for high excitation powers.
  • Shula L. Chen, Weimin M. Chen, Fumitaro Ishikawa, Irina A. Buyanova
    SCIENTIFIC REPORTS 5 11653  2015年06月 [査読有り][通常論文]
     
    III-V semiconductor nanowires (NWs) such as GaAs NWs form an interesting artificial materials system promising for applications in advanced optoelectronic and photonic devices, thanks to the advantages offered by the 1D architecture and the possibility to combine it with the main-stream silicon technology. Alloying of GaAs with nitrogen can further enhance performance and extend device functionality via band-structure and lattice engineering. However, due to a large surface-to-volume ratio, III-V NWs suffer from severe non-radiative carrier recombination at/near NWs surfaces that significantly degrades optical quality. Here we show that increasing nitrogen composition in novel GaAs/GaNAs core/shell NWs can strongly suppress the detrimental surface recombination. This conclusion is based on our experimental finding that lifetimes of photo-generated free excitons and free carriers increase with increasing N composition, as revealed from our time-resolved photoluminescence (PL) studies. This is accompanied by a sizable enhancement in the PL intensity of the GaAs/GaNAs core/shell NWs at room temperature. The observed N-induced suppression of the surface recombination is concluded to be a result of an N-induced modification of the surface states that are responsible for the nonradiative recombination. Our results, therefore, demonstrate the great potential of incorporating GaNAs in III-V NWs to achieve efficient nano-scale light emitters.
  • P. Patil, T. Tatebe, Y. Nabara, K. Higaki, N. Nishii, S. Tanaka, F. Ishikawa, S. Shimomura
    e-Journal of Surface Science and Nanotechnology 13 469 - 473 2015年 [査読有り][通常論文]
     
    Multi-quantum wells (MQWs) consisting of 3 or 3.5 pairs of nominally 8.8-nm-thick GaAs layers and 5.6-nmthick GaAs0.97Bi0.03 were grown by molecular beam epitaxy with varying the growth temperature of GaAs layers, TGaAs, and keeping the growth temperature of the GaAsBi layers at 350°C and their Bi compositional structure and optical properties were investigated. Analysis of x-ray diffraction spectra reveals that 67% of the total Bi atoms supplied during growth of a single GaAsBi layer were segregated on the growing surface and were incorporated into the successive GaAs layer at TGaAs = 350°C. The GaAs layers at TGaAs = 450 and 500°C contained 17% of the Bi atoms totally supplied and 50% of them were evaporated. Almost all Bi atoms segregated during growth of GaAsBi evaporated and were not incorporated into the GaAs layer at TGaAs = 550°C or higher. Photoluminescence (PL) spectra at 13 K shows all MQW samples have good optical quality and the MQW sample grown at TGaAs = 550°C shows the longest wavelength emission peak at 1116 nm which is 44 nm longer than the PL wavelength for the MQW grown at TGaAs = 350°C, even though the tremendous reduction of Bi incorporation into the GaAs layer grown at TGaAs = 550°C. The result strongly suggests that GaAsBi/GaAs has the type II band configuration.
  • S. L. Chen, S. Filippov, Fumitaro Ishikawa, W. M. Chen, I. A. Buyanova
    APPLIED PHYSICS LETTERS 105 25 253106  2014年12月 [査読有り][通常論文]
     
    Radiative carrier recombination processes in GaAs/GaNAs core/shell nanowires grown by molecular beam epitaxy on a Si substrate are systematically investigated by employing micro-photoluminescence (mu-PL) and mu-PL excitation (mu-PLE) measurements complemented by time-resolved PL spectroscopy. At low temperatures, alloy disorder is found to cause localization of photo-excited carriers leading to predominance of optical transitions from localized excitons (LE). Some of the local fluctuations in N composition are suggested to lead to strongly localized three-dimensional confining potential equivalent to that for quantum dots, based on the observation of sharp and discrete PL lines within the LE contour. The localization effects are found to have minor influence on PL spectra at room temperature due to thermal activation of the localized excitons to extended states. Under these conditions, photo-excited carrier lifetime is found to be governed by non-radiative recombination via surface states which is somewhat suppressed upon N incorporation. (C) 2014 AIP Publishing LLC.
  • Hideaki Hibi, Masahito Yamaguchi, Naold Yamamoto, Fumitaro Ishikawa
    NANO LETTERS 14 12 7024 - 7030 2014年12月 [査読有り][通常論文]
     
    Semiconductor/oxide composite nanowires (NWs) were synthesized by molecular beam epitaxial growth and subsequent wet oxidation. Nonselective and selective oxidation conditions applied to the GaAs/AlGaAs core-shell NWs grown on silicon substrates produced GaOx/AlGaOx and GaAs/AlGaOx NWs, respectively. The oxidized amorphous AlGaOx shell produced cathodoluminescence over a wide spectral range encompassing ultraviolet and visible wavelengths, possibly sourced from molecular species related to oxygen. The wire core was buried in the oxides when the diameter of the oxide shell increased, forming a planar structure. These composites are expected to pave the way to future electrical and optical functions for NWs.
  • Fumitaro Ishikawa, Hiroaki Goto, Masato Morifuji
    APPLIED PHYSICS EXPRESS 7 11 112003  2014年11月 [査読有り][通常論文]
     
    We investigated the use of dielectric-rod photonic crystals on a tensile-strained dilute nitride gain medium. After applying the patterned photonic crystal rods to GaInNAs quantum wells with a heterostructure having optical confinement, we observed enhanced extracted luminescence efficiency from the surface depending on the correlated variation in the transverse magnetic photonic band structure. (C) 2014 The Japan Society of Applied Physics.
  • ナノスケール結晶成長による新機能半導体材料の創出
    石川史太郎
    月刊 愛媛ジャーナル 137 80  2014年06月 [査読有り][通常論文]
  • Namsoo Ahn, Yoshiaki Araki, Masahiko Kondow, Masahito Yamaguchi, Fumitaro Ishikawa
    JAPANESE JOURNAL OF APPLIED PHYSICS 53 6 065001  2014年06月 [査読有り][通常論文]
     
    We investigate fundamental issues on the growth of GaAs/GaAsN core-shell heterostructure nanowires (NWs) by plasma-assisted molecular beam epitaxy. A Ga catalyst crystallizes during growth interruption at a high As pressure, and afterwards the growth dominantly progresses mainly increasing the NW diameter, thereby forming a wire shell. The shell diameter increases linearly depending on growth time and group III flux, similarly to the growth mechanism of planar layers. The lateral growth rate is 0.19 times lower than the growth rate of planar GaAs on a (100) substrate. At a substrate temperature 570 degrees C, nitrogen incorporation is inefficient in the shell layer. At a substrate temperature of 430 degrees C, the nitrogen is effectively introduced under continuous plasma irradiation during the growth of the GaAsN shell, resulting in the introduction of nitrogen within the shell estimated up to about 0.5%. (C) 2014 The Japan Society of Applied Physics
  • S. Nishimoto, M. Kondow, F. Ishikawa
    Journal of Vacuum Science & Technology B 32 2 02C121  2014年03月 [査読有り][通常論文]
     
    The authors measured reflection high-energy electron diffraction patterns during the formation of nitrogen delta-doped layers on GaAs(001). The authors investigated the effects of nitrogen coverage, substrate temperature, and growth rate of the GaAs overlayer on the roughness, faceting, and strain state of the surface. During delta-doping, the authors observed coherently grown nitrogen-mediated surface reconstruction. The lattice of the GaAs overlayer expanded and shrank as it grew up to two monolayers, eventually recovering to a smooth surface. When the GaAs overlayer was grown on d-doped layers with nitrogen coverage greater than 0.3 monolayers, it exhibited characteristic faceting, possibly caused by the presence of excess nitrogen adatoms. These behaviors were mostly identical for layers grown under both As-4 and As-2 overpressures. (C) 2014 American Vacuum Society.
  • Norihisa Nishimoto, Masahiko Kondow, Fumitaro Ishikawa
    Journal of Vacuum Science and Technology B:Nanotechnology and Microelectronics 32 2 2014年 [査読有り][通常論文]
     
    The authors measured reflection high-energy electron diffraction patterns during the formation of nitrogen δ-doped layers on GaAs(001). The authors investigated the effects of nitrogen coverage, substrate temperature, and growth rate of the GaAs overlayer on the roughness, faceting, and strain state of the surface. During δ-doping, the authors observed coherently grown nitrogen-mediated surface reconstruction. The lattice of the GaAs overlayer expanded and shrank as it grew up to two monolayers, eventually recovering to a smooth surface. When the GaAs overlayer was grown on δ-doped layers with nitrogen coverage greater than 0.3 monolayers, it exhibited characteristic faceting, possibly caused by the presence of excess nitrogen adatoms. These behaviors were mostly identical for layers grown under both As4 and As2 overpressures. © 2014 American Vacuum Society.
  • Hiroaki Goto, Fumitaro Ishikawa, Masato Morifuji, Masahiko Kondow
    JAPANESE JOURNAL OF APPLIED PHYSICS 52 10 105502  2013年10月 [査読有り][通常論文]
     
    We investigate the effect of micro-fabrication process damage on the photoluminescence characteristics of laser structures containing a GaInNAs and GaInAs quantum wells. By varying the size of the fabricated island structure, its impact on the photoluminescence intensity is studied. The GaInAs sample shows a strong decrease in its intensity with the reduction of the island size. In contrast, a slight increase is observed from the GaInNAs sample. This indicates the negligible impact of surface recombination on the GaInNAs sample, as well as the optical confinement within the micrometer-size island structure. The results suggest the feasibility of a GaInNAs gain medium for application to microfabricated optical devices. (C) 2013 The Japan Society of Applied Physics
  • Yuta Kitabayashi, Masaya Mochizuki, Fumitaro Ishikawa, Masahiko Kondow
    Japanese Journal of Applied Physics 52 4 04CG07  2013年04月 [査読有り][通常論文]
     
    We investigate inductively coupled plasma deep dry etching of Al 0.8Ga0.2As for photonic crystal (PC) fabrication using the Cl2, BCl3, and CH4 mixture. On the basis of our previous work [M. Mochizuki et al.: Jpn. J. Appl. Phys. 50 (2011) 04DG15], we explore the deeper dry etching of the PC structure, investigating the impact of gas flow rate and chemical reactions. Increasing gas flow rate and process pressure resulted in deeper etching. These conditions increased the self-bias applied on the sample, which induced the sharpening of the air hole bottom and limitation of further deep etching because of the strong contribution of physical etching. The reduction of CH4 gas suppressed the sidewall passivation, counteracting the effect of the physical etching. As a result, we obtained a PC structure having air holes with a depth larger than 1.5 μm and a diameter of 120 nm. © 2013 The Japan Society of Applied Physics.
  • K. Sumiya, M. Morifuji, Y. Oshima, F. Ishikawa
    Applied Physics Express 6 4 041002  2013年04月 [査読有り][通常論文]
     
    Using molecular beam epitaxy, we fabricate a superlattice structure having periodically arranged delta-doped nitrogen within GaAs. X-ray diffraction indicates the formation of regularly arranged 0.1ML delta-doped nitrogen having a certain dispersion every 3.7 nm, multilayered up to 10 periods. Optical transition energies obtained from photoreflectance reflect the number of superlattice periods. That suggests the formation of minibands in the short-period GaAsN/GaAs quantum wells, as well as the dispersed distribution of the nitrogen about similar to 7ML as also predicted from transmission electron microscopy. (C) 2013 The Japan Society of Applied Physics
  • Yoshiaki Araki, Masahito Yamaguchi, Fumitaro Ishikawa
    NANOTECHNOLOGY 24 6 065601  2013年02月 [査読有り][通常論文]
     
    The concept of band engineering dilute nitride semiconductors into nanowires is introduced. Using plasma-assisted molecular beam epitaxy, dilute nitride GaAsN/GaAs heterostructure nanowires are grown on silicon (111) substrates. Growth of the nanowires under high As overpressure results in a regular wire diameter of 350 nm with a length exceeding 3 mu m. The GaAsN/GaAs nanowires show characteristics including favorable vertical alignment, hexagonal cross-sectional structure with {110} g facets, regions of wurtzite and zinc-blende phases, and a core-shell-type heterostructure. The nanowires are composed of GaAsN shells containing up to 0.3% nitrogen surrounding GaAs cores. Panchromatic cathodoluminescence images show intensity modulation along the length of the nanowires that is possibly related to the interfaces of wurtzite/zinc-blende regions. Photoluminescence with peak wavelengths between 870 and 920 nm is clearly observed at room temperature. The spectral red shift depends on the amount of introduced nitrogen. These results reveal a method for precise lattice and band engineering of nanowires composed of dilute nitride semiconductors.
  • K. Higashi, S. Hasegawa, D. Abe, Y. Mitsuno, S. Komori, F. Ishikawa, M. Ishimaru, H. Asahi
    APPLIED PHYSICS LETTERS 101 22 221902-1 - 4 2012年11月 [査読有り][通常論文]
     
    We report on the coherent growth of GaGdN with high Gd concentration on a GaN template using radio-frequency plasma-assisted molecular beam epitaxy under elevated growth conditions. X-ray diffraction and cross-sectional transmission electron microscopy observations revealed that at a growth temperature of 700 degrees C or below, GaGdN layers are coherently grown on the GaN templates without segregation of the secondary phases. As the GdN mole fraction x was increased to 0.08, the c-axis lattice parameter in Ga1-xGdxN increased linearly. Increasing the growth temperature to 750 degrees C causes lattice relaxation in GaGdN. All GaGdN samples exhibited photoluminescence emissions near the band-edge, a blue luminescence band emission, and a green luminescence band emission. The origin of the green luminescence band emission is discussed in relation to the compressive strain existing in the GaGdN layers coherently grown on GaN. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4767992]
  • Akio Watanabe, Fumitaro Ishikawa, Masahiko Kondow
    JAPANESE JOURNAL OF APPLIED PHYSICS 51 5 056501-1 - 5 2012年05月 [査読有り][通常論文]
     
    We investigate the effects of inductively coupled O-2 plasma ashing, capacitively coupled C3F8 plasma etching, and capacitively coupled C3F8/O-2 plasma etching on the optical and electrical characteristics of GaAs-related optical device structures. The O-2 plasma ashing produces non radiative recombination centers close to the sample surface. The sample with a cap AlGaAs layer prevents the degradation of photoluminescence (PL) intensity, probably inhibiting the penetration of damaging ions into the buried quantum well. The C3F8 plasma etching also degrades the PL intensity; however, under moderate conditions, the effect of non radiative surface recombination can be suppressed by the formation of a surface oxide layer. On the other hand, the formation of oxide increases the specific contact resistance (rho(c)) of the electrode. The etching with C3F8/O-2 mixed plasma also deteriorates the optical characteristics presumably owing to the synthesized impact of the constituent gases, while it has limited effect on rho(c). (C) 2012 The Japan Society of Applied Physics
  • R. Gargallo-Caballero, E. Luna, F. Ishikawa, A. Trampert
    Applied Physics Letters 100 17 171906-1 - 4 2012年04月 [査読有り][通常論文]
     
    The local element distribution across tensile-strained N delta-doped (In,Ga)As/GaAs quantum wells (QWs) is investigated by transmission electron microscopy. The sub-monolayer (ML) insertion results in a several monolayers thick (In,Ga)(As,N) layer with lateral composition fluctuations. We also find an inhomogeneous In incorporation across the QW, with a minimum In content, [In](min), exactly at the position of the N-insertion, where N content is maximum, [N](max). Regardless of the position along the QW, [N](max) corresponds to [In](min) so that an (In, Ga)(As, N) layer of this composition has a lattice parameter close to a(GaAs). The impact of tensile strain on this complex chemical configuration is discussed. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4705731]
  • H. Nagatomo, K. Kukita, H. Goto, R. Nakao, K. Nakano, F. Ishikawa, M. Morifuji, M. Kondow
    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 30 2 2012年03月 [査読有り][通常論文]
     
    The authors demonstrated the functionality of a circularly arranged submicron scale optical cavity with a GaInNAs gain medium and an AlOx cladding layer within a two-dimensional photonic crystal slab. The GaInNAs gain has negligible optical degradations due to process damage, probably stemming from the suppressed diffusion carriers and the small surface recombination velocity of the material. The calculated spectrum when using a finite different time domain simulation provides a cavity mode containing a whispering gallery mode at a wavelength close to 1.3 mu m. An observation of the tuned spectral peaks related to the cavity mode shows this cavity has promise for future device applications. (C) 2012 American Vacuum Society. [http://dx.doi.org/10.1116/1.3691651]
  • Shin-ichiro Furuse, Kengo Sumiya, Masato Morifuji, Fumitaro Ishikawa
    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 30 2 2012年03月 [査読有り][通常論文]
     
    The authors carry out delta-doping at the middle of AlGaAs/GaAs quantum wells employing molecular beam epitaxy and varying the nitrogen coverage up to 0.5 monolayers. Transmission electron micrography and x ray diffraction indicate the introduction of a nitrogen delta-doped layer with precisely controlled position and nitrogen coverage. Photoluminescence spectra obtained for the samples show clear redshift of spectral peak positions depending on the amount of nitrogen, suggesting the band structure is modified by the delta-doping. The growth can be carried out at a substrate temperature of 560 degrees C. The growth temperature, which is high compared with that of standard dilute nitride compounds, could suppress the formation of growth-induced defects, resulting in the weak effect of post-growth thermal annealing on the characteristics of room-temperature photoluminescence. (C) 2012 American Vacuum Society. [DOI:10.1116/1.3678204]
  • Fumitaro Ishikawa, Shinichiro Furuse, Kengo Sumiya, Akihiro Kinoshita, Masato Morifuji
    JOURNAL OF APPLIED PHYSICS 111 5 053512-1 - 4 2012年03月 [査読有り][通常論文]
     
    We study energy-band engineering with nitrogen delta (delta)-doping in GaAs-related quantum structures. A tight-binding calculation indicates that the band structure can be engineered by introducing the one-dimensional doping profile of nitrogen into GaAs. Using molecular beam epitaxy, we prepare delta-doped samples of AlGaAs/GaAs quantum wells and GaAs/delta-doped nitrogen superlattice structures at the growth temperature 560 degrees C. Photoluminescence obtained from the samples shows a clear redshift of the spectral peak positions dependent on the nitrogen coverage. The transition energies of the superlattice structures agree well with those obtained from photoreflectance, indicating the feasibility of band modification with a single or a multiple nitrogen d-doped layer. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3691239]
  • Yuichiro Hirai, Takahiro Yamada, Masahiko Kondow, Fumitaro Ishikawa
    JAPANESE JOURNAL OF APPLIED PHYSICS 51 2 02BG10-1 - 4 2012年02月 [査読有り][通常論文]
     
    We investigate the characteristics of oxide film obtained by wet oxidation of AlxGa1-xAs with its Al concentration x between 0.55 and 0.99. 300-nm-thick AlxGa1-xAs grown on GaAs substrate by molecular beam epitaxy is wet-oxidized in a furnace at 410 degrees C for 120 min. Samples having x greater than 0.8 are confirmed to be oxidized from their observation, examined by X-ray diffraction showing the vanished crystallographic diffraction peaks. Scanning electron microscopy, X-ray reflectivity, and spectroscopic ellipsometry study determines the thickness, density and refractive index of the oxide films. (C) 2012 The Japan Society of Applied Physics
  • Masahiko Kondow, Fumitaro Ishikawa
    Advances in Optical Technologies 2012 754546  2012年 [査読有り][通常論文]
     
    GaInNAs was proposed and created in 1995. It can be grown pseudomorphically on a GaAs substrate and is a light-emitting material with a bandgap energy that corresponds to near infrared. By combining GaInNAs with GaAs, an ideal band lineup for laser-diode application is achieved. This paper presents the reproducible growth of high-quality GaInNAs by molecular beam epitaxy. Examining the effect of nitrogen introduction and its correlation with impurity incorporation, we find that Al is unintentionally incorporated into the epitaxial layer even though the Al cell shutter is closed, followed by the concomitant incorporation of O and C. A gas-phase-scattering model can explain this phenomenon, suggesting that a large amount of Ngas causes the scattering of residual Al atoms with occasional collisions resulting in the atoms being directed toward the substrate. Hence, the reduction of the sublimated Al beam during the growth period can suppress the incorporation of unintentional impurities, resulting in a highly pure epitaxial layer. © 2012 Masahiko Kondow and Fumitaro Ishikawa.
  • Shin-Ichiro Furuse, Kengo Sumiya, Masato Morifuji, Fumitaro Ishikawa
    Journal of Vacuum Science and Technology B:Nanotechnology and Microelectronics 30 2 02B117-1 - 5 2012年 [査読有り][通常論文]
     
    The authors carry out δ-doping at the middle of AlGaAs/GaAs quantum wells employing molecular beam epitaxy and varying the nitrogen coverage up to 0.5 monolayers. Transmission electron micrography and x ray diffraction indicate the introduction of a nitrogen δ-doped layer with precisely controlled position and nitrogen coverage. Photoluminescence spectra obtained for the samples show clear redshift of spectral peak positions depending on the amount of nitrogen, suggesting the band structure is modified by the δ-doping. The growth can be carried out at a substrate temperature of 560 ° C. The growth temperature, which is high compared with that of standard dilute nitride compounds, could suppress the formation of growth-induced defects, resulting in the weak effect of post-growth thermal annealing on the characteristics of room-temperature photoluminescence. © 2012 American Vacuum Society.
  • H. Nagatomo, K. Kukita, H. Goto, R. Nakao, K. Nakano, F. Ishikawa, M. Morifuji, M. Kondow
    Journal of Vacuum Science and Technology B:Nanotechnology and Microelectronics 30 2 02B127-1 - 4 2012年 [査読有り][通常論文]
     
    The authors demonstrated the functionality of a circularly arranged submicron scale optical cavity with a GaInNAs gain medium and an AlOx cladding layer within a two-dimensional photonic crystal slab. The GaInNAs gain has negligible optical degradations due to process damage, probably stemming from the suppressed diffusion carriers and the small surface recombination velocity of the material. The calculated spectrum when using a finite different time domain simulation provides a cavity mode containing a whispering gallery mode at a wavelength close to 1.3 m. An observation of the tuned spectral peaks related to the cavity mode shows this cavity has promise for future device applications. © 2012 American Vacuum Society.
  • Kentaro Kukita, Hiroshi Nagatomo, Hiroaki Goto, Ryo Nakao, Katsunari Nakano, Masaya Mochizuki, Masahiko Kondow, Masato Morifuji, Fumitaro Ishikawa
    JAPANESE JOURNAL OF APPLIED PHYSICS 50 10 2011年10月 [査読有り][通常論文]
     
    We investigate the function of a circularly arranged submicron-scale optical cavity having a GaInNAs gain medium introduced into a twodimensional photonic crystal slab. GaInNAs gain shows negligible optical degradations due to process damage, probably because of the small surface recombination velocity of the material. The preserved optical property realizes the observation of spectral peaks related to the cavity mode at wavelengths close to 1.3 mu m. Moreover, the cavity shows fine tunability of its characteristics via the deliberate adjustment of its structure. (C) 2011 The Japan Society of Applied Physics
  • Fumitaro Ishikawa, Masato Morifuji, Kenichi Nagahara, Masayuki Uchiyama, Kotaro Higashi, Masahiko Kondow
    JOURNAL OF CRYSTAL GROWTH 323 1 30 - 34 2011年05月 [査読有り][通常論文]
     
    We investigate the band gap engineering with sub-monolayer nitrogen introduction (: N delta-doping) at the middle of InGaAs/GaAs quantum well. Using plasma-assisted molecular beam epitaxy, we prepare samples varying the introduced nitrogen between 0 and 0.4 monolayer. The growths are carried out at substrate temperature of 520 degrees C, comparatively higher than conventional substrate temperature for dilute nitride compounds. This induces the roughening of the growth front, slightly enhancing the nitrogen incorporation within the crystal. The as-grown and annealed samples show clear room temperature photoluminescence, indicating the band gap shrinkage depending on the amount of nitrogen. (C) 2010 Elsevier B.V. All rights reserved.
  • Hiroki Nakamoto, Fumitaro Ishikawa, Masahiko Kondow, Yushi Ohshima, Atsushi Yabuuchi, Masataka Mizuno, Hideki Araki, Yasuharu Shirai
    JAPANESE JOURNAL OF APPLIED PHYSICS 50 4 2011年04月 [査読有り][通常論文]
     
    We study the annealing behavior of GaNAs by positron annihilation spectroscopy and photoluminescence spectroscopy. The introduction of nitrogen reduces the S-parameter of the material, which is further lowered by annealing. Moreover, the samples show typical optical characteristics of the GaNAs system. The results suggest that the observed reduction of the S-parameter is not simply due to the reduction of vacancy-type defects, but could be related to the characteristic carrier localization in this material system. (C) 2011 The Japan Society of Applied Physics
  • Masaya Mochizuki, Yuta Kitabayashi, Tomoya Nakajima, Daiki Satoi, Fumitaro Ishikawa, Masahiko Kondow, Makoto Hara, Chiharu Kimura, Hidemitsu Aoki, Takashi Sugino
    JAPANESE JOURNAL OF APPLIED PHYSICS 50 4 2011年04月 [査読有り][通常論文]
     
    We investigate inductively coupled plasma deep dry etching of Al(0.8)Ga(0.)2As for photonic crystal (PC) fabrication using Cl-2, BCl3, and CH4 chemistry. The characteristic AlOx deposition is observed during the etching, resulting in the reduction of etching rate. BCl3 is considered to scavenge the deposited AlOx by its reductive reaction. CH4 passivates the etching sidewall, as well as enhances the deposition of AlOx. Concerning the impact of pattern size, a pronounced inverse reactive ion etching (RIE) lag is observed, which is beneficial for small-size PC fabrication typically with a hole diameter of 100-500nm. From the findings, we successfully fabricated a PC structure with air holes having an aspect ratio of 8 and a diameter of 110nm. (C) 2011 The Japan Society of Applied Physics
  • F. Ishikawa, S. Fuyuno, K. Higashi, M. Kondow, M. Machida, H. Oji, J. -Y. Son, A. Trampert, K. Umeno, Y. Furukawa, A. Wakahara
    APPLIED PHYSICS LETTERS 98 12 2011年03月 [査読無し][通常論文]
     
    Using bulk sensitive hard x-ray photoelectron spectroscopy, we directly observe a spectrum related to N-As bonding defects in (Ga,In)(N,As)/Ga(N,As) heterostructure. The defects are most likely attributed to split interstitials. Their concentration is in the order of 10(19) cm(-3), close to the detection limit of the measurement. Rapid thermal annealing eliminates the defects, leading to those undetectable. Similar phenomenon is observed for N-P bonding defects in In (N,P). The results indicate common features in dilute nitride semiconductor system: existence of N-(group V) bonding defects and their behavior on postgrowth annealing. (C) 2011 American Institute of Physics. [doi:10.1063/1.3573789]
  • Shuichi Emura, Hiroki Nakamoto, Fumitaro Ishikawa, Masahiko Kondow, Hajime Asahi
    PHYSICS OF SEMICONDUCTORS: 30TH INTERNATIONAL CONFERENCE ON THE PHYSICS OF SEMICONDUCTORS 1399 41 - 42 2011年 [査読有り][通常論文]
     
    Introducing normal coordinate system, theoretical approach to band gap alteration with temperature is described. The derived expression is applied to a GaNAs system having the nitrogen composition of about 1.4%. It is found that the band gap narrowing in this system is originated in the inter-band mixing assisted by an LO phonon at a Gamma point through electron - phonon interaction.
  • K. Umeno, Y. Furukawa, N. Urakami, S. Mitsuyoshi, H. Yonezu, A. Wakahara, F. Ishikawa, M. Kondow
    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 28 3 2010年05月 [査読有り][通常論文]
     
    The authors have investigated the growth and luminescence properties of InPN alloys grown by solid-source molecular-beam epitaxy (MBE). The N composition increases with decreasing growth rate, P-2/In flux ratio, and growth temperature. In this work, the highest N composition obtained is 0.56% for the InPN sample. The appropriate growth temperature is around 400 degrees C. However, the growth-temperature window of the InPN alloys having a smooth surface is very narrow. In order to obtain photoluminescence (PL) emission from the InPN samples grown by solid-source MBE, InPN alloys must be grown under the condition of lower-plasma power since the grown-in point defects induced by N plasma are reduced. Thermal treatment is effective to improve the luminescence efficiency of InPN alloys, and the appropriate annealing temperature is around 700 degrees C. However, the S-shape behavior is observed only for the annealed InPN samples by atomic rearrangements during thermal treatment, which is attributed to the weaker bond strength of In-N than that of In-P. In addition, the PL peak energy corresponding to the near-band edge emission redshifts with increasing annealing temperature. These results indicate that the luminescence properties of InPN alloys are unique in contrast to other dilute nitrides such as GaAsN and GaPN alloys.
  • Kotaro Higashi, Fumitaro Ishikawa, Katsumi Handa, Shuichi Emura, Masahiko Kondow
    REVIEW OF SCIENTIFIC INSTRUMENTS 81 4 2010年04月 [査読有り][通常論文]
     
    We propose a simple sample preparation technique of x-ray absorption fine structure (XAFS) for its application to the individual layer of practical compound semiconductor devices. An epitaxial lift-off process enables the investigation of pure uppermost thin epitaxial layer without containing information of the bottom-side layers as well as substrate. The plain procedure offers smooth thin film with desired thickness preserving its crystallographic structure, suitable for the measurement. We carry out XAFS measurements for 2.0 and 0.2 mu m thick GaAs epitaxial layer at transmission and fluorescence mode, respectively. Clear extended-XAFS oscillation is obtained, and the radial distribution function of which deduces accurate first nearest-neighbor Ga-As bond length to be 2.46 A degrees for both the samples. That shows the feasibility of the proposed technique for the analysis of the precise atomic configurations of thin film semiconductors.
  • K. Umeno, Y. Furukawa, N. Urakami, S. Mitsuyoshi, H. Yonezu, A. Wakahara, F. Ishikawa, M. Kondow
    Journal of Vacuum Science and Technology B:Nanotechnology and Microelectronics 28 3 C3 - B26 2010年 [査読無し][通常論文]
     
    The authors have investigated the growth and luminescence properties of InPN alloys grown by solid-source molecular-beam epitaxy (MBE). The N composition increases with decreasing growth rate, P2 /In flux ratio, and growth temperature. In this work, the highest N composition obtained is 0.56% for the InPN sample. The appropriate growth temperature is around 400 °C. However, the growth-temperature window of the InPN alloys having a smooth surface is very narrow. In order to obtain photoluminescence (PL) emission from the InPN samples grown by solid-source MBE, InPN alloys must be grown under the condition of lower-plasma power since the grown-in point defects induced by N plasma are reduced. Thermal treatment is effective to improve the luminescence efficiency of InPN alloys, and the appropriate annealing temperature is around 700 °C. However, the S-shape behavior is observed only for the annealed InPN samples by atomic rearrangements during thermal treatment, which is attributed to the weaker bond strength of In-N than that of In-P. In addition, the PL peak energy corresponding to the near-band edge emission redshifts with increasing annealing temperature. These results indicate that the luminescence properties of InPN alloys are unique in contrast to other dilute nitrides such as GaAsN and GaPN alloys. © 2010 American Vacuum Society.
  • Masahiko Kondow, Fumitaro Ishikawa, Kazuyuki Umeno, Yuzo Furukawa, Akihiro Wakahara
    APPLIED PHYSICS EXPRESS 3 1 2010年 [査読有り][通常論文]
     
    The infrared (IR) absorption spectra of InN(x)P(1-x) (x = 0.19-0.56%) grown on an InP substrate are investigated by Fourier-transform infrared (FT-IR) spectroscopy. The optical phonon corresponding to the In-N bond in InNP has an energy of 456 cm(-1). This energy matches the reported value for the optical phonon energy of In-N bonds in GaInNAs. It is very close to the transverse optical (TO) phonon energy in pure cubic InN. It contrasts with the fact that the optical phonon energy of Ga-N bonds in GaInNAs is lower by 85 cm(-1) in comparison with the TO phonon energy in pure cubic GaN. Thermal annealing hardly affects the phonon spectrum of InNP, although it improves the crystallinity of the semiconductor. (C) 2010 The Japan Society of Applied Physics
  • Shudong Wu, Yongge Cao, Stanko Tomic, Fumitaro Ishikawa
    JOURNAL OF APPLIED PHYSICS 107 1 2010年01月 [査読有り][通常論文]
     
    The optical gain and radiative current density of GaInNAs/GaAs/AlGaAs separate confinement heterostructure quantum well (QW) lasers with an emission wavelength of 1.3 mu m have been theoretically investigated. The effect of carrier leakage from the GaInNAs QW to the GaAs waveguide layer is studied, and its influence on the optical gain and radiative current density is identified. The hole filling caused by an injected carrier has a strong impact on the optical gain and radiative current density, while the effect of electron filling is negligible, reflecting the smaller band-gap discontinuity in the valence band than in the conduction band. Hole occupation in the waveguide layer decreases the optical gain, and increases the radiative and threshold current densities of the laser. Our calculated threshold current density (659.6 A/cm(2)) at T=300 K is in good agreement with the experimental value (650.9 A/cm(2)) reported in literature [R. Fehse , IEEE J. Sel. Top. Quantum Electron. 8, 801 (2002)].
  • Fumitaro Ishikawa, Shudong Wu, Masakazu Kato, Masayuki Uchiyama, Kotaro Higashi, Masahiko Kondow
    JAPANESE JOURNAL OF APPLIED PHYSICS 48 12 2009年12月 [査読有り][通常論文]
     
    Introduction of nitrogen gas induces inefficient Al beam termination when the shutter closes during molecular beam epitaxy. In spite of the closed shutter of the Al cell, the epitaxial layer contains Al at a concentration (n(Al)) of over 10(18) cm(-3). This depends on the vapor pressures of N(2) (P(N2)) and Al (P(Al)) as n(Al) proportional to P(N2) P(Al). An analytical model considering gas phase scattering reproduce the dependences, suggesting that a large amount of N(2) gas causes the scattering of residual Al atoms with an occasional collision resulting in the atoms directed toward the substrate. Possible impacts on the epitaxial layer, caused by the Al incorporation and related phenomena, are also discussed. The scattering of Al, and its getter effect on other elements especially O can cause further undesirable incorporation of impurities within the epitaxial layer. (C) 2009 The Japan Society of Applied Physics
  • R. Kudrawiec, P. Poloczek, J. Misiewicz, F. Ishikawa, A. Trampert, K. H. Ploog
    JOURNAL OF APPLIED PHYSICS 106 3 2009年08月 [査読無し][通常論文]
     
    The temperature dependencies of optical transitions in as-grown Ga0.64In0.36N0.046As0.954 multiple quantum wells (QWs) of various widths (ranging from 3.9 to 8.1 nm) grown at the low temperature of 375 degrees C were studied by photoreflectance (PR). In addition to the 11H transition, which is the fundamental transition for this QW, the optical transitions between excited states (22H and 33H transitions, where the notation klH denotes the transition between the kth heavy-hole valence subband and the lth conduction subband) were clearly observed in the PR spectra. The temperature dependencies of the QW transition energies were analyzed using Varshni and Bose-Einstein expressions. It was found that with increasing temperature, both the ground-state and the excited-state transitions shift to the red without showing S-shape-type behaviors, which are typical for photoluminescence from this system. This shift does not depend on the QW width and amounts to similar to 80 meV for the 11H transition and similar to 100 meV for the 22H and 33H transitions in the temperature range of 10-300 K. These shifts are comparable to those of N-free QWs.
  • Masayuki Uchiyama, Fumitaro Ishikawa, Masahiko Kondow
    JAPANESE JOURNAL OF APPLIED PHYSICS 48 8 0811021 - 0811024 2009年08月 [査読有り][通常論文]
     
    We undertake an exclusive study on the plasma-assisted molecular-beam epitaxy of GaNAs, focusing on plasma conditions. We investigate the effects of species contributing to growth and the ions produced on the resulting structural and optical characteristics of the epitaxial layer, and the effect of rapid thermal annealing on the layer. The larger the RF power, the larger the amount of both atomic N and metastable molecule N-2* are produced, resulting in a monotonic increase in nitrogen incorporation. An increase in the nitrogen gas flow rate leads to the saturation of nitrogen incorporation, followed by a reduction in atomic N. Both atomic N and metastable molecule N-2* contribute to the growth. The number of ions produced is larger at a larger RF power and lower nitrogen gas flow rate, but is almost negligible near the border of the plasma mode transition. The sample exposed to fewer ions during growth shows better optical properties. (C) 2009 The Japan Society of Applied Physics
  • E. Luna, F. Ishikawa, B. Satpati, J. B. Rodriguez, E. Tournie, A. Trampert
    JOURNAL OF CRYSTAL GROWTH 311 7 1739 - 1744 2009年03月 [査読無し][通常論文]
     
    Transmission electron microscopy (TEM) techniques are applied to characterize the interfaces of epitaxial III-V semiconductor heterostructures with high spatial resolution and to analyze compositional variations at interfaces. As expected, realistic interfaces of compound semiconductors are not chemically sharp but there is a transition region at the interface. The functional dependence of the smooth change in composition is sigmoidal and can be described using an analytical expression, thus enabling a quantitative characterization of the interface width. The model gives a very good description of the distribution profiles and applies to several material systems, including the interfaces of As-based alloys and those of the non-common-atom InAs/GaSb short-period superlattices. The analysis of (Ga,In)(N,As)/GaAs quantum wells reveals that there is a connection between the interface properties in this material system and the miscibility gap of the alloy. (C) 2008 Elsevier B.V. All rights reserved.
  • A. Guzman, E. Luna, F. Ishikawa, A. Trampert
    JOURNAL OF CRYSTAL GROWTH 311 7 1728 - 1732 2009年03月 [査読無し][通常論文]
     
    A comparative study of the influence of Sb and N ion concentration on the Properties of GaInNAs (GINA) quantum wells (QWs) is presented. We find that for perfect two-dimensional (2D) QW there is no direct perceptible improvement in structural quality due to the introduction of Sb. Moreover, contrast variations in the QW suggest an inhomogeneous Sb incorporation. A different behaviour of the integrated photoluminescence (PL) intensity with temperature is observed when comparing the 2D samples grown with/without Sb. Regarding the GINA QWs exhibiting a three-dimensional (3D) morphology, we observe a significant improvement in structural quality for the samples grown with added Sb, as well as for those Sb-free samples but grown under a low N- ions density. Nevertheless, 2D and 3D samples show clear common properties: the GINA:Sb QWs exhibit an improved PL efficiency, but only at high temperatures. On the contrary, the Sb-free samples grown under a low N- ions concentration exhibit a brighter PL at all temperatures considered. (C) 2008 Elsevier B.V. All rights reserved.
  • F. Ishikawa, S. D. Wu, M. Kato, M. Uchiyama, K. Higashi, M. Kondow
    JOURNAL OF CRYSTAL GROWTH 311 7 1646 - 1649 2009年03月 [査読無し][通常論文]
     
    We examine unintentional incorporation of Al during the growth of molecular beam epitaxy (MBE) related to N gas introduction. In spite of the closed shutter of Al cell, we observe Al incorporation in the epitaxial layer with a concentration up to 1 x 10(18) cm(-3). The concentration depends on the N(2) gas flow rate and Al source temperature. The concentration is suppressed by the reduction of the Al cell temperature. Shutter control of the N cell, As beam equivalent pressure and the operation of the RF plasma Power have no impact on that. The introduction of the large amount of N can modify the beam dispersion of Al in the MBE chamber, which will cause the extrinsic Al incorporation. The unintentional impurity incorporation can induce material deteriorations. We thus suggest that the growth should be carried out with the decreased Al cell temperature and the N gas flow rate as low as possible. (C) 2008 Elsevier B.V. All rights reserved.
  • Robert Kudrawiec, Grzegorz Sek, Jan Misiewicz, Fumitaro Ishikawa, Achim Trampert, Klaus H. Ploog
    APPLIED PHYSICS LETTERS 94 1 2009年01月 [査読有り][通常論文]
     
    Optical transitions in GaNAs bulk layer containing 2.2% N have been studied with microphotoluminescence (mu-PL) and photoreflectance. At low temperatures and low excitation conditions, the mu-PL spectra showed sharp PL lines of 100-300 mu eV widths about 10-20 meV below the energy gap. Those lines were attributed to the recombination of localized excitons trapped at local potential minima. When the excitation power was increased, an additional smooth PL band appeared at the higher-energy side. This band corresponds to the light-hole transition in photoreflectance spectrum, i.e., transition between the delocalized states.
  • Fumitaro Ishikawa, Alvaro Guzman, Oliver Brandt, Achim Trampert, Klaus H. Ploog
    JOURNAL OF APPLIED PHYSICS 104 11 2008年12月 [査読有り][通常論文]
     
    Using photoluminescence (PL) spectroscopy, we carry out a comparative study of the optical properties of (Ga,In) (N,As) and (Ga,In) (N,As,Sb) quantum wells. The incorporation of Sb into (Ga,In) (N,As) results in a reduced quantum efficiency at low temperatures but an improved one at room temperature (RT). A PL line shape analysis as well as the temperature dependence of the PL peak energy reveals the existence of band-tail localized states in both material systems. The carrier localization energy is larger for (Ga,In) (N,As,Sb) than for (Ga,In) (N,As), leading to a longer radiative lifetime and thus a reduced quantum efficiency at low temperatures for the former material. The thermal quenching of the quantum efficiency is analyzed by a rate equation model, which shows that the density of nonradiative centers is reduced in (Ga,In) (N,As,Sb) resulting in an enhanced quantum efficiency at RT. (c) 2008 American Institute of Physics.
  • E. Luna, F. Ishikawa, P. D. Batista, A. Trampert
    APPLIED PHYSICS LETTERS 92 14 2008年04月 [査読無し][通常論文]
     
    The indium distribution across (Ga,In)(N,As) quantum wells is determined by using transmission electron microscopy techniques. Inside the quantum well, the indium distribution is well described by Muraki's segregation model; however, it fails in reflecting the concentration at the interfaces. To describe them, we propose a sigmoidal law which defines the smooth variation of the indium concentration with the position and provides a systematic and quantitative characterization of the interfaces. The thermal stability of the interfaces and their interplay with segregation effects are discussed. A connection between the high thermal robustness of the interfaces and the inherent thermodynamic miscibility gap of the alloy is suggested. (C) 2008 American Institute of Physics.
  • Shudong Wu, Masakazu Kato, Masayuki Uchiyama, Kotaro Higashi, Fumitaro Ishikawa, Masahiko Kondow
    APPLIED PHYSICS EXPRESS 1 3 0350041 - 0350043 2008年03月 [査読有り][通常論文]
     
    We report the unintentional incorporation of Al during the growth of molecular beam epitaxy using RF plasma source, driven by N(2) gas flow. The concentrations of N, Al, O, and C within GaNAs/GaAs/AlAs structure are investigated by secondary ion mass spectrometry. In spite of the closed shutter of Al cell, we observe Al incorporation with a concentration up to 1 X 10(18) cm(-3) in GaNAs layer and characteristically in the bottom side GaAs. Its concentration is solely dependent on N2 gas flow rate. Remarkably, the operation of the RF plasma has no impact on that. C and O show their concentrations corresponding to,the extrinsic Al. The complex interactions between those elements predict a possible origin of material deteriorations and difficulty for the precise doping control. (C) 2008 The Japan Society of Applied Physics.
  • T. Ikari, S. Fukushima, Y. Ohta, A. Fukuyama, S. D. Wu, F. Ishikawa, M. Kondow
    PHYSICAL REVIEW B 77 12 2008年03月 [査読無し][通常論文]
     
    The band gap and exciton binding energies of dilute nitride Ga(1-y)In(y)N(0.012)As(0.988) films with the thickness of 100 nm were determined as a function of indium composition for investigating the effect of strain on the electronic band structure. The high sensitive piezoelectric photothermal (PPT) methodology was used for measuring the optical absorption spectra. The fitting analysis was carried out to eliminate the influence of exciton and to determine precisely the band gap energy using the three dimensional direct allowed transition models with the Voigt function as a convolution profile. Comparing experimental result with the theoretical prediction for the strain free structures, the hydrostatic and shear deformation potentials were determined as -7.0 and -1.7 eV, respectively. We found that the shear deformation potential is almost the same as that for GaAs, conflicting to the reported results for GaNAs. The results demonstrated that the present PPT method is worth for investigating the effect of strain on the electronic structures of the dilute nitride semiconductor thin film structure.
  • S. D. Wu, M. Kato, M. Uchiyama, K. Higashi, F. Ishikawa, M. Kondow
    PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 5, NO 9 5 9 2736 - 2739 2008年 [査読有り][通常論文]
     
    We report the effect of unintentional Al incorporation during the growth of GaInNAs/GaAs quantum well (QW) by molecular beam epitaxy (MBE). The effect of extrinsic Al is investigated by secondary ion mass spectrometry. QW grown directly on AlAs layer shows unintentionally incorporated Al with its concentration as high as 1 x 10(18) cm(-3), resulting in de-graded PL intensity. In order to prevent the Al incorporation, we grow QW without heating up Al source after leaving the MBE chamber within As atmosphere for a long period. The concentration of the extrinsic Al becomes lower than 2x10(16) cm(-3), leading to a strong PL intensity. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • S. D. Wu, M. Kato, M. Uchiyama, K. Higashi, F. Ishikawa, M. Kondow
    Physica Status Solidi (C) Current Topics in Solid State Physics 5 9 2736 - 2739 2008年 [査読無し][通常論文]
     
    We report the effect of unintentional Al incorporation during the growth of GaInNAs/GaAs quantum well (QW) by molecular beam epitaxy (MBE). The effect of extrinsic Al is investigated by secondary ion mass spectrometry. QW grown directly on AlAs layer shows unintentionally incorporated Al with its concentration as high as 1x1018 cm-3resulting in degraded pl intensity. In order to prevent the al incorporation, we grow qw without heating up al source after leaving the mbe chamber within as atmosphere for a long period. The concentration of the extrinsic al becomes lower than 2x10 16 cm-3, leading to a strong pl intensity.© 2008 Wiley-VCH Verlag GmbH & Co. KGaA.
  • Fumitaro Ishikawa, Achim Trampert, Klaus H. Ploog
    Journal of Crystal Growth 301 529 - 533 2007年04月 [査読有り][通常論文]
     
    We investigate the molecular beam epitaxial growth (MBE) of (Ga,In)(N,As) multiple quantum wells at a low substrate temperature and under low As pressure. The advantages of this growth concept to achieve 1.55 μ m emissions are as follows: (i) the low growth temperature prevents composition modulations, leading to abrupt heterointerfaces; (ii) the low As pressure allows the introduction of a large amount of N in the layers due to the reduced competition for incorporation of group V elements; (iii) reducing the As pressure counteracts the effect of the low growth temperature, thus improving photoluminescence intensity. With this concept, (Ga,In)(N,As) quantum well emitting at 1.55 μ m are successfully grown in two MBE systems, equipped with different As source configurations. © 2006 Elsevier B.V. All rights reserved.
  • Robert Kudrawiec, Marta Gladysiewicz, Jan Misiewicz, Fumitaro Ishikawa, Klaus H. Ploog
    APPLIED PHYSICS LETTERS 90 4 2007年01月 [査読有り][通常論文]
     
    The optical transitions of as-grown Ga0.64In0.36N0.046As0.954 multiple quantum wells grown at the low temperature of 375 degrees C were studied by contactless electroreflectance (CER). The investigation was carried out at room temperature for a set of samples having quantum well (QW) widths ranging from 3.9 to 8.1 nm. The ground and the excited state transitions were clearly observed in CER spectra (the ground state transition was observed at the wavelength of 1.9 mu m for the 8.1 nm wide QW). The experimental QW transition energies were compared with theoretical predictions based on an effective mass formalism model. Good agreement between experimental data and theoretical calculations has been obtained assuming that the conduction band offset for GaInNAs/GaAs interface is 80% and the electron effective mass is 0.09m(0). (c) 2007 American Institute of Physics.
  • Fumitaro Ishikawa, Esperanza Luna, Achim Trampert, Klaus H. Ploog
    Applied Physics Letters 89 18 2006年10月 [査読有り][通常論文]
     
    The authors discuss the effect of substrate temperature and As beam equivalent pressure (BEP) on the molecular beam epitaxial growth of (Ga,In)(N,As) multiple quantum wells (MQWs). Transmission electron microscopy studies reveal that a low substrate temperature essentially prevents composition modulations. Secondary ion mass spectrometry results indicate that a low As BEP reduces the incorporation competition of group V elements. The low substrate temperature and low As BEP growth condition leads to (Ga,In)(N,As) MQWs containing more than 4% N preserving good structural and optical properties, and hence demonstrating 1.55 μm photoluminescence emission at room temperature. © 2006 American Institute of Physics.
  • F. Ishikawa, K. J. Friedland, H. Kostial, K. H. Ploog
    Physica Status Solidi C: Conferences 3 623 - 626 2006年05月08日 [査読無し][通常論文]
     
    The electron transport in Ga(As,N) layers is investigated focusing on the influence of potential fluctuations. A metal-insulator transition is observed with increasing electron concentration, in the temperature dependence of the resistivity for a series of samples with 0.8% and 1.7% of N. The observed behavior is discussed in the frame of Anderson transition. A quantitative value for the percolation threshold Vp, at which the transport characteristics will change, is obtained by considering a chemical potential and an activation energy. The large Vp, can explain the thermally activated conductivity which can be observed even up to 300 K. We observe an increase of Vp by increasing the N concentration up to 2.2%. V p can be efficiently reduced by rapid thermal annealing for samples with higher N concentration. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA.
  • F Ishikawa, M Horicke, U Jahn, A Trampert, KH Ploog
    APPLIED PHYSICS LETTERS 88 19 2006年05月 [査読無し][通常論文]
     
    We grow high-quality (Ga,In)(N,As) quantum wells containing 36% In and 4.5% N by molecular beam epitaxy, with a low As pressure and low substrate temperature growth concept. A V/III beam equivalent pressure ratio of 5 and a substrate temperature of 375 degrees C lead to highly regular ten-period multiple quantum well structures having abrupt interfaces and smooth surfaces. By varying the quantum well width from 4 to 8 nm, we observe 1.34-1.6 mu m emission of narrow linewidth (<= 50 meV) at room temperature after annealing. The large conduction band offset of 410 meV estimated from calculations is beneficial for a material system considered for high temperature laser operation. (c) 2006 American Institute of Physics.
  • F Ishikawa, KJ Friedland, H Kostial, KH Ploog
    PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 3 NO 3 3 3 623 - + 2006年 [査読有り][通常論文]
     
    The electron transport in Ga(As,N) layers is investigated focusing on the influence of potential fluctuations. A metal-insulator transition is observed with increasing electron concentration, in the temperature dependence of the resistivity for a series of samples with 0.8% and 1.7% of N. The observed behavior is discussed in the frame of Anderson transition. A quantitative value for the percolation threshold V, at which the transport characteristics will change, is obtained by considering a chemical potential and an activation energy. The large V, can explain the thermally activated conductivity which can be observed even up to 300 K. We observe an increase of V, by increasing the N concentration up to 2.2%. V-p can be efficiently reduced by rapid thermal annealing for samples with higher N concentration. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Wemheim.
  • F Ishikawa, G Mussler, KJ Friedland, H Kostial, K Hagenstein, L Daweritz, KH Ploog
    APPLIED PHYSICS LETTERS 87 26 1 - 3 2005年12月 [査読無し][通常論文]
     
    We investigate the electron transport in Ga(As,N) layers focusing on the influence of potential fluctuations. With increasing electron concentration, a metal-insulator transition is observed in the temperature dependence of the resistivity for a series of samples containing 0.8% of N. The observed behavior is discussed in the frame of Anderson transition. By increasing the N concentration up to 2.2%, we observe an increase of the potential fluctuations' amplitude. Mean-square values for the intrinsic N-induced fluctuation gamma(N) are obtained from percolation theory to be larger than 30 meV. Rapid thermal annealing reduces gamma(N) significantly for samples with higher N concentration. These large potential fluctuations lead to electron localization and induce thermally activated conductivity which is observable up to 300 K. (c) 2005 American Institute of Physics.
  • T Oikawa, F Ishikawa, T Sato, T Hashizume, H Hasegawa
    APPLIED SURFACE SCIENCE 244 1-4 84 - 87 2005年05月 [査読無し][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.
  • F Ishikawa, T Oikawa, T Hashizume, H Hasegawa
    2004 INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE AND RELATED MATERIALS, CONFERENCE PROCEEDINGS 548 - 551 2004年 [査読有り][通常論文]
     
    The cathodoluminescence in-depth spectroscopy (CLIS) technique is applied to GaN-based and GaAs-based structures as a new method of non-destructive in-depth and in-plane characterization. Here, a plot of CL intensity vs. acceleration voltage is defined as the CLIS spectrum, and it is analyzed on computer. Detailed recombination dynamics for band edge emission and yellow luminescence in GaN and AlGaN/GaN materials was clarified by comparing experimental and theoretical CLIS spectra. The method was also successfully applied to in-depth and in-plane characterization of an AlGaAs/GaAs three-dimensionally inter-crossing quantum wire structure, giving information on geometry and alloy composition.
  • F Ishikawa, H Hasegawa
    APPLIED SURFACE SCIENCE 212 885 - 889 2003年05月 [査読無し][通常論文]
     
    Cathodoluminescence in-depth spectroscopy (CLIS) study was made on GaN and AlGaN/GaN materials. The experimental CLIS spectra were compared with analysis on computer. The calculation reproduces experimentally observed CLIS spectrum shapes remarkably well. High density U-shaped surface states with particular charge neutrality levels should exist on the surface of the GaN layer to account for observed finite onset voltage and stretching of CLIS spectra. AlGaN layer seems to act like a surface passivation layer for GaN leading to band edge emission with a nearly ideal CLIS spectrum shape with negligible recombination at heterointerface. Yellow luminescence is due to deep acceptor levels uniformly distributed in the GaN bulk where radiative transition from conduction band edge to deep acceptors gives luminescence. (C) 2003 Elsevier Science B.V. All rights reserved.
  • T Kakumu, F Ishikawa, S Kasai, T Hashizume, H Hasegawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 42 4B 2230 - 2236 2003年04月 [査読無し][通常論文]
     
    For the <001>-oriented In0.5Ga0.5P/GaAs beterostructure grown by gas source molecular beam epitaxy (GSMBE) using tertiarybutylphosphine (TBP), presence of the natural ordering of group III atoms and its effect on heterointerface properties are investigated for the first time. Using in situ reflection high energy electron diffraction (RHEED) observation and photoluminescence (PL) measurements, growth temperature and growth sequence were optimized to grow high-quality InGaP layers with defect-free heterointerfaces. By PL measurements on <001>- and <311>-oriented samples simultaneously grown under the same growth conditions, existence of natural ordering in <001>-oriented samples was found. The so-called long-range order parameter, eta, of the InGaP layer increased with increase of the TBP flow rate and with decrease of the growth rate. 77 could be changed in the range of 0.06-0.29 by changing the growth conditions, corresponding to the band gap change of 43 meV. The valence band offset (DeltaE(V)) measured by in situ XPS method was 0.29 eV and was independent of the value of eta. The change of conduction band offset (DeltaE(C)) due to ordering caused a corresponding change in the sheet carrier density of two-dimensional electron gas at the heterointerface. No significant contribution from piezoelectric or spontaneous polarization was seen up to q = 0.29.
  • F. Ishikawa, H. Hasegawa
    Physica Status Solidi C: Conferences 7 2707 - 2711 2003年 [査読無し][通常論文]
     
    Cathodoluminescence in-depth spectroscopy (CLIS) study was made at room temperature on a thick GaN sample. In experiments, CLIS spectra for near band edge (NBE) emission and yellow luminescence (YL) were observed, and their theoretical spectra were calculated on computer. The comparison between theory and experiment indicated that the YL center is a deep acceptor which is spatially uniformly distributed within the GaN layer, that surface recombination plays an important role in the overall recombination statistics, and that the major non-radiative recombination process is that of high density excitons even at room temperature. © 2003 WILEY-VCH Verlag GmbH & Co. KGaA.
  • F Ishikawa, H Hasegawa
    APPLIED SURFACE SCIENCE 190 1-4 508 - 512 2002年05月 [査読無し][通常論文]
     
    As a new approach for contactless and non-destructive characterization method of buried multi-layer heterointerfaces, acceleration voltage-dependence of cathodoluminescence (CL) spectra is investigated for various InGaP/GaAs multi-layer heterostructures. The plot of CL intensity vs. acceleration voltage for a multi-layer heterostructure is defined as the cathodoluminescence in-depth spectrum (CLIS). Experimental CLIS spectra on InGaP/GaAs single heterostructures and quantum well structures grown on GaAs by MOVPE and by GSMBE using TBP as the P source demonstrate that CLIS technique is very powerful to obtain depth-resolved information on multi-layer heterostructures. (C) 2002 Elsevier Science B.V. All rights reserved.
  • 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 [査読無し][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.
  • F Ishikawa, A Hirama, H Hasegawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 40 4B 2769 - 2774 2001年04月 [査読無し][通常論文]
     
    InGaP/GaAs heterostructures were grown by gas source molecular beam epitaxy (GSMBE) using tertiarybutylphosphine (TBP), and their bulk and interface deep levels were studied by deep level transient spectroscopy (DLTS), photoluminescence (PL), and cathodoluminescence (CL) techniques. Five bulk deep levels related to phosphorus vacancies and their complexes were detected by DLTS. They could be almost completely removed under a TBP flow rate higher than 4-5 seem, accompanied by a marked increase of the bulk band edge PL intensity. On the other hand, InGaP/GaAs heterostructures grown under high TBP flow rates showed anomalous PL and CL peaks near 1.7 eV. CL study performed by changing the acceleration voltage showed that these peaks were heterointerface related, most likely due to phosphorus vacancies near interfaces. InGaP/GaAs quantum wells (QW) without such peaks and with intense QW emission were successfully formed by avoiding phosphorous vacancy formation through elimination of growth interruption.
  • H Fujikura, A Hirama, F Ishikawa, H Sai, H Hasegawa
    2000 INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE AND RELATED MATERIALS, CONFERENCE PROCEEDINGS 372 - 375 2000年 [査読有り][通常論文]
     
    From FL, CL and DLTS measurements, several bulk and interface deep levels were detected in the InGaP epitaxial layers and the InGaP/GaAs quantum wells (QWs) grown by TBP-based GSMBE. These bulk deep levels were almost completely removed by the growth under large TBP flow rate. These bulk deep levels seem to be related to phosphorous vacancy (Vp) Or Vp-related complex. On the other hand, InGaP-on-GaAs hetero-interface formed with finite growth interruption exhibited anomalous PL emission at around 1.7 eV. A defect due to strained InGaAsP interlayer at the InGaP-on-GaAs interface produced by the growth interruption is likely to be responsible for the anomalous emission. Anomalous emission was suppressed drastically by the growth without interruption. Intense and narrow PL emissions due to the QWs themselves were observed for the QWs grown without growth interruption.

書籍

  • Strategic Molecular Beam Epitaxial Growth of GaAs/GaAsBi Heterostructures and Nanostructures
    Pallavi Kisan Patil, Satoshi Shimomura, Fumitaro Ishikawa, Esperanza Luna, Masahiro Yoshimoto (担当:共著範囲:Chapter 4. in Bismuth-Containing Alloys and Nanostructures, edited by Shumin Wang and Pengfei Lu)
    Springer 2019年07月 (ISBN: 9789811380778) 38 pp. 59-96
  • GaAs/AlGaOx Heterostructured Nanowires
    Fumitaro Ishikawa, Naoki Yamamoto (担当:共著範囲:Chapter 8 in Novel Compound Semiconductor Nanowires - Materials, Devices, and Applications, edited by Fumitaro Ishikawa and Irina A. Buyanova, pp. 255-290)
    Pan Stanford Publishing 2017年09月
  • Dilute Bismide Nanowires
    Wojciech M. Linhart, Szymon J. Zelewski, Fumitaro Ishikawa, Satoshi Shimomura, Robert Kudrawiec (担当:共著範囲:Chapter 5 in Novel Compound Semiconductor Nanowires - Materials, Devices, and Applications, edited by Fumitaro Ishikawa and Irina A. Buyanova, pp. 161-176)
    Pan Stanford Publishing 2017年09月
  • GaNAs-Based Nanowires for Near-Infrared Optoelectronics
    Irina A. Buyanova, Fumitaro Ishikawa, Weimin M. Chen (担当:共著範囲:Chapter 4 in Novel Compound Semiconductor Nanowires - Materials, Devices, and Applications, edited by Fumitaro Ishikawa and Irina A. Buyanova, pp. 133-160)
    Pan Stanford Publishing 2017年09月
  • Novel Compound Semiconductor Nanowires - Materials, Devices, and Applications
    Fumitaro Ishikawa, Irina A. Buyanova (担当:編者(編著者))
    Pan Stanford Publishing 2017年09月 (ISBN: 9789814745765) 548

講演・口頭発表等

  • 2-inch wafer scale optically efficient GaAs nanowire ensembles on Si  [招待講演]
    Fumitaro Ishikawa
    Pacifichem 2021: The 2021 International Chemical Congress of Pacific Basin Societies 2021年12月
  • OPTICALLY EFFICIENT III-V COMPOUND SEMICONDUCTOR NANOWIRES ON SI  [招待講演]
    Fumitaro Ishikawa
    The 30th IEEE Asian Test Symposium 2021 (ATS 2021) 2021年11月 口頭発表(基調)
  • 超高真空中でよく観察されるひげ結晶そしてナノワイヤ  [招待講演]
    石川史太郎
    2021年第82回応用物理学会秋季学術講演会 2021年09月 口頭発表(招待・特別)
  • Molecular beam epitaxial growth of III-V-bismide semiconductors at low temperatures toward terahertz and optical device applications  [招待講演]
    Yoriko Tominaga, Fumitaro Ishikawa, Kouichi Akahane
    8th International Workshop Epitaxial Growth and Fundamental Properties of Semiconductor Nanostructures (SemiconNano2021) 2021年09月
  • III-V族半導体を用いた電子ビーム源デバイスが切り拓く微細領域の産業技術  [招待講演]
    T. Nishitani, Y. Honda, M. Araidai, H. Amano, M. Tabuchi, A. Narita, H. Yasuda, F. Ishikawa, T. Meguro, A. Koizumi, D. Sato, A. Honda
    第39回電子材料シンポジウム 2020年10月 口頭発表(招待・特別)
  • 希釈窒素・ビスマスナノワイヤの分子線エピタキシャル成長  [招待講演]
    石川史太郎
    日本結晶成長学会ナノエピ分科会「第12回ナノ構造・エピタキシャル成長講演会」 2020年07月 口頭発表(招待・特別)
  • ナノスケール融合電子材料の開拓  [招待講演]
    石川史太郎
    日本材料学会 半導体エレクトロニクス委員会 第1回特別研究会 2020年02月 口頭発表(招待・特別)
  • Extending Compound Semiconductor Nanowire Functions by the Introduction of Additional Elements  [招待講演]
    Fumitaro Ishikawa
    The AVS Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2018) 2018年12月 口頭発表(招待・特別)
  • Low-dimensional quantum structure formation in GaAs/GaAsBi core-multishell nanowires  [招待講演]
    Fumitaro Ishikawa, Kosuke Yano, Kyohei Takada, Pallavi Patil, Satoshi Shimomura, Yumiko Shimizu
    The 9th International Workshop on Bismuth-Containing Semiconductors 2018年07月 口頭発表(招待・特別)
  • GaAs/GaNAs core/shell nanowires - a promising platform for nanoscale optoelectronics  [招待講演]
    S. L. Chen, M. Jansson, F. Ishikawa, W. M. Chen, I. A. Buyanova
    Nanowire Week 2018 2018年06月 口頭発表(招待・特別)
  • Epitaxial nanowires/microstructures exploring next generation electronics  [招待講演]
    Fumitaro Ishikawa
    STINT/JSPS (The Swedish Foundation for International Cooperation in Research and Higher Education/The Japanese Society for the Promotion of Science) summer workshop 2017 2017年08月 口頭発表(招待・特別)
  • Looking for extra compound semiconductor nanowires  [招待講演]
    Fumitaro Ishikawa
    International Workshop on Advanced Smart Materials and Engineering for Nano- and Bio-Technologies 2017年07月 口頭発表(招待・特別)
  • GaAsBiナノワイヤの分析  [招待講演]
    石川史太郎, 赤松良彦, 渡辺健太郎, 上杉文彦, 朝比奈俊輔, Uwe Jahn, 下村哲
    平成28年度 文部科学省ナノテクノロジープラットフォーム総会, 第2部 H27年度の秀でた利用成果事例紹介 2016年10月
  • Additional GaAs related nanowires  [招待講演]
    Fumitaro Ishikawa
    JSPS workshop on Japan-Sweden frontiers in spin and photon functionalities of semiconductor nanostructures 2016年08月 口頭発表(招待・特別)
  • Novel GaNAs and GaNP-Based Nanowires ・Promising Materials for Optoelectronics and Photonics  [招待講演]
    Irina Buyanova, Fumitaro Ishikawa, Charles Tu, Weimin Chen
    IEEE NANO 2016- 16th International Conference On Nanotechnology 2016年08月 口頭発表(招待・特別)
  • GaAsBi Heterostructured Nanowires Grown by Molecular Beam Epitaxy  [招待講演]
    Fumitaro Ishikawa, Satoshi Shimomura
    The 7th International Workshop on Bismuth-Containing Semiconductors 2016年07月 口頭発表(招待・特別)
  • Additional compound semiconductor nanowires for photonics  [招待講演]
    Fumitaro Ishikawa
    SPIE Photonics West 2016 2016年02月 口頭発表(招待・特別)
  • 化合物半導体エピタキシャル成長を基盤とした新機能ナノワイヤ材料の開拓  [招待講演]
    石川史太郎
    新化学技術推進協会, 先端化学・材料技術部会 新素材分科会講演会 2016年02月 公開講演,セミナー,チュートリアル,講習,講義等
  • Exploring additional functions of GaAs-related nanowires  [招待講演]
    Fumitaro Ishikawa
    PACIFICHEM 2015 2015年12月 口頭発表(招待・特別)
  • Semiconductor/oxide composite nanowires supplying white luminescence  [招待講演]
    F. Ishikawa, N. Yamamoto
    The 228th ECS Meeting 2015年10月 口頭発表(招待・特別)
  • Compound semiconductor/oxide composite nanowire system  [招待講演]
    石川史太郎
    BIT's 4th Annual World Congress of Nano Science and Technology 2014年10月
  • 窒化物MBEにおける基礎検討事項:~GaAs系結晶成長との比較から~  [招待講演]
    石川史太郎
    平成26年度 文部科学省ナノテクノロジープラットフォーム 微細構造解析プラットフォーム 第1回放射光利用研究セミナー 2014年09月
  • 化合物半導体ナノワイヤを基盤とした新光電変換材料探索  [招待講演]
    石川史太郎
    平成26年度 第39回 太陽光発電プロジェクト講演会 2014年03月

共同研究・競争的資金等の研究課題

  • 超高圧合成透明ナノセラミックス
    日本学術振興会:科学研究費助成事業 基盤研究(A)
    研究期間 : 2021年04月 -2026年03月 
    代表者 : 入舩 徹男
  • 光通信を革新する新希釈窒素・希釈ビスマス量子ナノ光源の開拓
    日本学術振興会:科学研究費助成事業 国際共同研究加速基金(国際共同研究強化(B))
    研究期間 : 2021年10月 -2025年03月 
    代表者 : 石川 史太郎
  • 低温成長による点欠陥密度の制御に基づくBi系Ⅲ-Ⅴ族半導体の発現機能の最大活用
    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 : 2021年04月 -2024年03月 
    代表者 : 富永 依里子
  • ナノワイヤ蛍光体による偏光白色LEDの開発
    キヤノン財団:研究助成プログラム「新産業を生む科学技術」
    研究期間 : 2020年04月 -2023年03月 
    代表者 : 石川史太郎
  • 半導体・酸化物複合ナノワイヤによる光・電子・スピン工学の融合
    日本学術振興会:科学研究費助成事業 基盤研究(A)
    研究期間 : 2019年04月 -2023年03月 
    代表者 : 石川 史太郎
     
    本研究では、「半導体・酸化物複合ナノワイヤ」の高品質合成とその応用で光・電子・スピンを操作した新しい学術・工学を開拓する。化合物半導体の高い電子・光物性と金属酸化物の多様で安定した機能が協働する高機能ナノ材料を提案し、これを用いたフォトニクス・エレクトロニクス・スピントロニクス融合型ナノテクノロジーの創出を目指す。初年度には、研究の基盤となるナノワイヤ試料合成技術の確立と高度化に取り組み、以下に挙げる成果を得ることができた。 まず、高品質GaAs/AlGaOx/TiOヘテロ構造ナノワイヤ作製に取り組んだ。大きな進展が得られた成果としては、2インチのSi基 板上に大面積で市販p型GaAsと同程度以上の発光強度を有するナノワイヤ群の成長に成功した。さらに、自然酸化を用いることでプロセスダメージのない状態でアモルファスAlGaO最外殻層をGaAsナノワイヤに形成できること、同AlGaOが適切に内部GaAsの光閉じ込め効果を発揮し、発光強度増強効果を得るとともに、年単位 でその特性を維持する保護層として有効であることを見出した。また、形成されたGaAsナノワイヤ最外殻にTiOをスパッタリングすることで、正確に膜厚制御されたTiOをコーティングしたGaAs/TiOコア-シェル型ナノワイヤが合成できることを確認した。近赤外域で動作する高い熱安定性や発熱の抑制が期待される希釈窒化物・希釈ビスマスIII-V属半導体ナノワイヤの合成を発展させ、特徴的なGaAsBi量子構造ナノワイヤを得ることにも成功した。
  • 実環境下の損傷敏感試料に微細領域の動態観測技術をもたらす半導体電子ビーム源
    日本学術振興会:科学研究費補助金: 基盤研究(A)
    研究期間 : 2019年04月 -2022年03月 
    代表者 : 西谷智博
  • 高温・高圧合成による次世代電子材料ダイヤモンドの創出
    池谷科学技術新興財団:研究助成
    研究期間 : 2020年04月 -2021年03月 
    代表者 : 石川史太郎
  • IoT社会を支える省エネルギー光通信用新規半導体レーザの開発
    中国電力技術研究財団:試験研究 (A)
    研究期間 : 2020年04月 -2021年03月 
    代表者 : 富永依里子
  • ビスマス系半導体半金属混晶の量子構造を活用した新規光学デバイスの開発
    村田学術振興財団:研究助成 (自然科学)
    研究期間 : 2019年06月 -2020年12月 
    代表者 : 富永依里子
  • 半導体・酸化物複合ナノワイヤ材料の確立と光触媒応用
    日本学術振興会:科学研究費補助金 若手研究(A)
    研究期間 : 2016年04月 -2020年03月 
    代表者 : 石川史太郎
  • ナノ多結晶半導体ダイヤモンド創出にむけた新規ドーピング技術の確立
    日本学術振興会:科学研究費補助金: 挑戦的研究(萌芽)
    研究期間 : 2017年04月 -2019年03月 
    代表者 : 石川史太郎
  • 高温・高圧合成によるキャリア制御型半導体ダイヤモンドの確立
    日本学術振興会: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 : 石川史太郎
  • 新エレクトロニクス材料としての化合物半導体/酸化物融合ナノワイヤ確立
    加藤科学振興会:研究助成
    研究期間 : 2015年 -2016年 
    代表者 : 石川史太郎
  • 半導体・酸化物融合による新材料ナノワイヤエレクトロニクスの創出
    村田学術振興財団:研究助成
    研究期間 : 2014年 -2015年 
    代表者 : 石川史太郎
  • 希釈窒化物半導体GaAsNナノワイヤの結晶成長とフォトニック結晶展開
    倉田記念日立科学技術財団:倉田奨励金
    研究期間 : 2013年04月 -2014年03月 
    代表者 : 石川史太郎
  • 希釈窒化物半導体光源を用いた誘電体ロッド型フォトニック結晶レーザの創出
    日本学術振興会:科学研究費補助金 若手研究(A)
    研究期間 : 2011年04月 -2014年03月 
    代表者 : 石川史太郎
  • 極薄窒化層導入による新手法半導体バンドエンジニアリングの創製
    光科学技術研究振興財団:研究助成
    研究期間 : 2010年 -2011年 
    代表者 : 石川史太郎

大学運営

委員歴

  • 2022年 - 現在   34th International Microprocesses and Nanotechnology Conference (MNC 2022)   Steering Committee Vice Chair
  • 2021年 - 現在   2022 International Conference on Solid State Devices and Materials (SSDM2022)   Program committee
  • 2019年 - 現在   日本金属学会   講演大会委員
  • 2014年 - 現在   電子材料シンポジウム   論文委員
  • 2021年 - 2022年   Compound Semiconductor Week 2022 (CSW-2022)   Program sub-committee
  • 2019年 - 2022年   応用物理学会中国四国支部   幹事
  • 2021年 - 2021年   日本結晶成長学会 第13回ナノ構造・エピタキシャル成長講演会   実行委員長
  • 2021年 - 2021年   34rd International Microprocesses and Nanotechnology Conference (MNC 2021)   Program committee, Sub section head
  • 2020年 - 2021年   2021 International Conference on Solid State Devices and Materials (SSDM2021)   Program committee
  • 2021年   日本結晶成長学会 ナノ構造・エピタキシャル成長分科会   幹事
  • 2020年 - 2020年   2020 International Conference on Solid State Devices and Materials (SSDM2020)   Program committee
  • 2020年 - 2020年   33rd International Microprocesses and Nanotechnology Conference (MNC 2020)   Program committee, Section head
  • 2020年 - 2020年   2020年日本表面真空学会学術講演会   実行委員
  • 2020年 - 2020年   日本結晶成長学会 第12回ナノ構造・エピタキシャル成長講演会   実行委員長
  • 2019年 - 2020年   応用物理学会   学術講演会 プログラム編集委員
  • 2016年 - 2020年   文部科学省 科学技術予測センター   専門調査員
  • 2019年 - 2019年   Science and Technology of Nano-Polycrystalline Diamond (STNPD) 2019   Organizing Committee
  • 2019年 - 2019年   32nd International Microprocesses and Nanotechnology Conference (MNC 2019)   Program committee, Section head
  • 2018年 - 2019年   2019 International Conference on Solid State Devices and Materials (SSDM2019)   Program committee
  • 2018年 - 2019年   EDISON 21 – The 21st International Conference on Electron Dynamics in Semiconductors, Optoelectronics and Nanostructures   Organizing committee
  • 2018年 - 2019年   Compound Semiconductor Week 2019   Program committee
  • 2018年 - 2019年   22nd International Vacuum Congress, 2022 (IVC-22) 準備委員会委員
  • 2018年 - 2019年   SemiconNano2019   Steering committee
  • 2018年 - 2018年   2nd JSPS workshop on Japan-Sweden frontiers in photon and spin functionalities of nanomaterials   Committee member
  • 2018年 - 2018年   9th International Workshop on Bismuth-Containing Semiconductors   Program committee
  • 2016年 - 2017年   第37回レーザー学会年次大会,徳島   プログラム委員
  • 2015年 - 2017年   電子材料シンポジウム   総務委員
  • 2016年 - 2016年   Compound Semiconductor Week 2016, Toyama, Indium Phosphide and Related Materials   Program committee
  • 2014年 - 2016年   文部科学省 科学技術動向研究センター   専門調査員
  • 2014年 - 2014年   第55回真空に関する連合講演会, 大阪   実行委員
  • 2013年 - 2013年   第33回レーザー学会年次大会,姫路   プログラム委員
  • 2011年 - 2013年   日本真空学会   関西支部幹事
  • 2012年 - 2012年   2012 International Symposium on Compound Semiconductors (ISCS-2012), Santa Barbara   Program committee
  • 2012年 - 2012年   17th International Conference on Molecular Beam Epitaxy (ICMBE-2012), Nara   Local arrangement committee
  • 2012年 - 2012年   第53回真空に関する連合講演会,神戸   実行委員
  • 2012年 - 2012年   The Collaborative Conference on Crystal Growth (3CG), Orland   Conference co-chairs
  • 2008年 - 2008年   Second International Symposium on Growth of III-Nitrides (ISGN-2), Izu   Executive committee
  • 2007年 - 2007年   Second International Symposium on Atomic Technology, Awaji   Organizing committee


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