論文 - 鈴木 秀俊
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Koto H., Kawano M., Suzuki H.
Japanese Journal of Applied Physics Part 1 Regular Papers and Short Notes and Review Papers 64 ( 4 ) 2025年4月
担当区分：最終著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Japanese Journal of Applied Physics Part 1 Regular Papers and Short Notes and Review Papers
In this study, to control the N distribution in GaAsN films, GaAsN/GaAs superlattice (SL)-structure films were grown by repeating one cycle of the GaAsN atomic layer growth sequence and n (0-9) cycles of the GaAs growth sequence using atomic layer epitaxy. The effects of n on the incorporation of N atoms into the GaAsN layer and the detailed N distribution in the film were investigated by considering the lattice constants of the GaAsN/GaAs SL and SL periods, as evaluated by X-ray diffraction. The formation of the SL structures was confirmed, although the SL periods deviated slightly from the designed values. The SL periods were not singular for the films and the direction of the SL period was slightly tilted (∼0.2°) from the growth direction. This indicates the existence of at least two regions with different tilt directions and periods in the film.
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T. Harada,S. Harada, H. Suzuki, S. Endo, A. Ogura, M. Imaizumi, T. Ikari, A. Fukuyama
Journal of Physics D: Applied Physics 58 ( 11 ) 2025年3月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Journal of Physics D: Applied Physics
To reduce fluctuations in the performance of lattice-mismatched solar cells within a wafer, it is necessary to characterize and quantify the effect of misfit dislocations, caused by strain relaxation, on the performance of a solar cell. To this end, the relationship between the preferential glide planes (GPs) and the carrier generation-recombination process in InGaAs solar cells with low (LowV) and high (HighV) open-circuit voltages has been investigated in this study. The GPs of the β dislocations in the HighV cells were uniformly controlled in the wafer plane. However, the LowV cells contained a mixture of two in-plane regions, in which the GPs of the β dislocations were controlled by the surface atomic steps during their growth on a vicinal substrate (LowV-sub region) or by the InGaP ordering effect (LowV-ord region). The results of the microwave photoconductivity decay method and our newly-developed laser heterodyne photothermal displacement method suggested that the photoexcited carrier concentration was low in the LowV-ord region. A photoluminescence measurement as a function of temperature further revealed that indium fluctuations occurred due to the presence of the GPs of the β dislocation. The LowV cells exhibited high indium composition and reduced bandgap. Thus, a small photoexcited carrier concentration and reduced bandgap energy decreased the difference between the quasi-Fermi levels of electrons and holes, resulting in a small VOC. The photovoltaic performance could be determined by the density of the threading dislocations and the corresponding fluctuations in the indium composition owing to the different GPs of the β dislocations.
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M. Kawano, T. Haraguchi, H. Suzuki
Journal of Crystal Growth 649 2025年1月
担当区分：最終著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Journal of Crystal Growth
The effects of nitrogen (N) distribution on the electrical properties of GaAsN films were evaluated by intentionally changing the N distribution using atomic layer epitaxy (ALE) and post-annealing. The N distribution was controlled in the growth direction by growing superlattice (SL) thin films repeatedly growing 1 GaAsN layer and 0, 3, and 5 layers of GaAs by ALE. These films were referred to as (1:0), (1:3), and (1:5), respectively. To change the N distribution in the same thin film, N atoms were diffused by post-annealing. Changes in N distribution were evaluated by X-ray diffraction as changes in GaAsN superstructure. N atoms diffused from GaAsN layers to the adjacent layers in (1:3) films annealed above 750 °C, while they remained stable in those of (1:5) films annealed at temperatures up to 850 °C. The carrier mobility of both films increased monotonically with the annealing temperature. The concentration of ionized scattering centers decreased significantly in films annealed at 650 °C (independent of their N distributions) owing to the elimination of donor-type defects by annealing. Contrarily, the concentrations of N-induced scattering centers in (1:5) films annealed below 900 °C were similar, while those in (1:3) films annealed above 750 °C decreased significantly, in agreement with the N-atom diffusion behavior of GaAsN layers. Thus, N-distribution homogenization can be related to the reduction of N-induced scattering centers.
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格子不整合系InGaAs 太陽電池における転位すべり面の向きが光励起キャリアの再結合に与える影響
原田 尚吾, 原田 知季, 鈴木 秀俊, 小倉 暁雄, 碇 哲雄, 福山 敦彦
宮崎大学工学部紀要 53 57 - 64 2024年10月
記述言語：日本語 掲載種別：研究論文（大学，研究機関等紀要） 出版者・発行元：宮崎大学工学部
Lattice-mismatched solar cells are known to have high conversion efficiency. However, their open-circuit voltages (VOC) are not uniformly distributed within a wafer due to the preferential glide plane of β dislocations. Furthermore, the effect of dislocations on the carrier recombination process is still under discussion. We investigated two types of InGaAs solar cells with the InGaP step-graded buffer layers grown on the vicinal GaAs substrate. The first cell showed a high VOC (HighV), and the preferential glide plane of β dislocations was well controlled using the vicinal substrate. The second cell had a low VOC (LowV), where the preferential glide planes of β dislocations were nonuniformly distributed within the cell due to the InGaP ordering effect. In this study, laser heterodyne photothermal displacement mappings, microwave photoconductivity decay mappings, and photoluminescence measurements were performed to discuss carrier recombination properties. In the HighV cell, almost uniform signal distributions were observed. On the other hand, the observed signals in the LowV cell were nonuniformly distributed. We also found that the obtained results of nonuniformity correspond to the distribution of preferential glide planes of β dislocations. These results indicate that the VOC reduction strongly depends on the direction of the preferential glide plane of β dislocations.
DOI： 10.34481/0002000816
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逆格子マッピング測定を用いた、格子不整合InGaAs太陽電池の転位滑り面の面内分布異方性の観察
鈴木 秀俊
九州シンクロトロン光研究センター利用報告書2023年度 2024年10月
担当区分：筆頭著者 記述言語：日本語 掲載種別：研究論文（大学，研究機関等紀要）
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Harada S., Suzuki H., Ogura A., Imaizumi M., Ikari T., Fukuyama A.
28th Microoptics Conference Moc 2023 2023年
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：28th Microoptics Conference Moc 2023
We investigated the relationships between the distribution of dislocation glide planes and carrier recombination properties in InGaAs solar cells with different open-circuit voltage (VOC) using microwave photoconductivity decay and photoluminescence measurements. The results showed the low VOC was due to the recombination of the photoexcited carriers with the dislocation-related defect.
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Ogura A., Nogawa S., Kawano M., Minematsu R., Suzuki H.
Applied Physics Express 14 011001 2020年12月
記述言語：英語 掲載種別：研究論文（学術雑誌）
By using synchrotron X-ray diffraction, we investigated the in-plane distribution of preferential glide planes in a metamorphic InGaAs solar cell with a relatively low open-circuit voltage (Voc) compared to other cells fabricated on the same wafer. The reciprocal-space maps revealed that the low-Voc cell contains several domains with different preferential glide planes of β dislocations. Since fluctuations of the average β-glide plane have not been observed for high-Voc cells, the observed inhomogeneous distribution should be related to the Voc degradation. Understanding preferential glide-plane changes within a cell can help to improve the uniformity of cell properties over the whole wafer.
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Ogura A., Yi W., Chen J., Suzuki H., Imaizumi M.
Journal of Electronic Materials 49 ( 9 ) 5219 - 5225 2020年9月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Journal of Electronic Materials
© 2020, The Minerals, Metals & Materials Society. Epitaxial growth of lattice-mismatched materials is useful for solar cells, but lattice dislocations must be controlled for best device performance. It has been shown that metamorphic growth enables fabrication of InGaAs p–n junctions with good performances on GaAs substrates due to the insertion of buffer layers. Here, we investigate misfit and threading dislocations inside the step-graded InGaP buffer layers of a single-junction InGaAs solar cell by cathodoluminescence microscopy. Prior to measurement, the device edges were polished at various angles (less than 10° with respect to the substrate surface). By using this technique, cross sections of very thin layers can be directly imaged with a resolution that allows us to observe misfit and threading dislocations. In the present device, the densities of the two types of dark lines depend on the position in the buffer structure. In particular, near the InGaAs base layer, the density of the dark lines extending in the [110] direction is higher than that of the dark lines extending in the [1-10] direction. We believe that this difference in the dark line density is related to the surface morphology.
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Suzuki H., Ishikawa F., Sasaki T., Takahasi M.
Applied Physics Express 13 ( 5 ) 2020年5月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Applied Physics Express
© 2020 The Japan Society of Applied Physics. We carry out real-time in situ synchrotron X-ray diffraction on the growth of GaN and AlN on SiC(0001) substrate by molecular beam epitaxy. At the initial growth stage of GaN/SiC or AlN/SiC heterostructure, the epitaxial overlayer develops affected by defects with the strain interaction between SiC, eventually showing characteristic lattice deformations. GaN was almost relaxed at the initial stage, showing the transition of the growth mode from 3D to 2D at around 4 nm. In contrast, AlN coherently grow on SiC(0001) at the initial stage for 13 nm concomitantly showing lattice deformation with the beneath SiC, subsequently showing gradual lattice relaxation.
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Kawano M., Minematsu R., Haraguchi T., Fukuyama A., Suzuki H.
Japanese Journal of Applied Physics 59 ( SG ) SGGF10 2020年4月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Japanese Journal of Applied Physics
© 2020 The Japan Society of Applied Physics. GaAsN films with different N distributions have been grown using the atomic layer epitaxy method to evaluate the effects of N distribution on the electrical properties of GaAsN. Three films, which had the same N composition with different N distribution were fabricated by alternate stack of GaAsN 1 monolayer (ML) and GaAs (0, 3, 5) ML. According to the X-ray diffraction measurement, periodicity and small N interdiffusion between GaAs and GaAsN layers in grown GaAsN films were confirmed. Thus, N distribution in the films were successfully modified in the order of a few unit lattice. Contribution of each scattering mechanisms on carrier mobility and densities of scattering centers in grown GaAsN films were evaluated. Compared with the film with 0 ML of GaAs, the density of N induced scattering center decreased with insertion of GaAs 3 ML between GaAsN 1 ML. It again increased the film with insertion of GaAs 5 ML. These results suggest that controlling N distribution intentionally not only degraded but also improved the electrical properties of GaAsN films.
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Ogura A., Suzuki H., Imaizumi M.
Journal of Crystal Growth 533 2020年3月
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Journal of Crystal Growth
© 2019 Elsevier B.V. Metamorphic growth of light absorber layers of solar cells introduces misfit dislocations due to strain relaxation, and their influences on the solar cell performance need to be characterized. In this work, we correlate the asymmetry of relaxation probabilities via different glide planes (which results in a tilt of the epilayer) with the open-circuit voltages (Voc) of several metamorphic InGaAs single junction solar cells. The devices contain graded InGaP buffer layers and are grown on a GaAs 001 wafer with a small miscut towards the 100 direction. We observe an inhomogeneous distribution of the solar cells’ Voc within the wafer and are able to correlate the Voc fluctuation to a difference in the asymmetry of the glide plane distributions of α and β dislocations. In the case of solar cells exhibiting a high Voc, the glide planes of both α and β dislocations are controlled by the surface orientation. In the case of low-Voc samples, the glide planes of the β dislocations are controlled by the ordering of InGaP, while those of the α dislocations are still controlled by the surface orientation.
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Ogura A., Nogawa S., Kawano M., Minematsu R., Kubo K., Imaizumi M., Suzuki H.
Applied Physics Express 14 ( 1 ) 2020年
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Applied Physics Express
By using synchrotron X-ray diffraction, we investigated the in-plane distribution of preferential glide planes in a metamorphic InGaAs solar cell with a relatively low open-circuit voltage (V oc) compared to other cells fabricated on the same wafer. The reciprocal-space maps revealed that the low-V oc cell contains several domains with different preferential glide planes of β dislocations. Since fluctuations of the average β-glide plane have not been observed for high-V oc cells, the observed inhomogeneous distribution should be related to the V oc degradation. Understanding preferential glide-plane changes within a cell can help to improve the uniformity of cell properties over the whole wafer.
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Inhomogenious distribution of misfit dislocations in metamorphic InGaAs solar cells
Shota Nogawa, Akio Ogura, Masahiro Kawano, Koushirou Kubo, Mitsuru Imaizumi, and Hidetoshi Suzuki
Abstract of the 19th international conference on solid films and surfaces 2019年10月
記述言語：英語 掲載種別：研究論文（研究会，シンポジウム資料等）
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Growth and Evaluation of GaAsN Films With Different N Distribution Grown by Atomic Layer Epitaxy
M. Kawano, R. Minematsu, T. Haraguchi, A. Fukuyama, H. Suzuki
Abstract of solid state devices and materials 2019 C-5-04 2019年9月
記述言語：英語 掲載種別：研究論文（研究会，シンポジウム資料等）
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その場X線回折測定を用いた GaAs(001)基板上InGaAs成長におけるIn偏析の解析 査読あり
鈴木 秀俊, 佐々木 拓生, 高橋 正光, 大下 祥雄
SPring-8/SACLA利用研究成果集 7 ( 2 ) 2019年8月
記述言語：日本語 掲載種別：研究論文（大学，研究機関等紀要）
分子線エピタキシー法を用いた GaAs(001) 基板上への InGaAs 薄膜成長中のIn偏析過程の解明を目指し、放射光を用いたX線回折法を用いてリアルタイム測定を行った。回折強度計算と実験結果との比較から、成長中の膜中の In 分布の変化を算出し、各時点での偏析係数を見積もった。成長速度が早い場合は (0.20, 0.27 ML/s)、一つの偏析係数で計算結果と実験結果が一致したが、成長速度が遅い場合 (0.10 ML/s) では一つの偏析係数で説明することが不可能であった。この結果は、特に成長速度が遅い場合において、これまでの偏析モデルを修正する必要を示唆している。
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Ogura A., Tanikawa T., Takamoto T., Oshima R., Suzuki H., Imaizumi M., Sugaya T.
Conference Record of the IEEE Photovoltaic Specialists Conference 273 - 276 2019年6月
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Conference Record of the IEEE Photovoltaic Specialists Conference
© 2019 IEEE. Lattice-mismatched materials enable growth of IIIV multi junction solar cells with band-gap combinations that are closer to the theoretical optimum than those of conventional material combinations. In order to improve material quality and hence conversion efficiency, it is important to reduce threading dislocations by employing graded buffer layers (GBLs) between subcells with different lattice constants. We have to understand how threading dislocations are formed from misfit dislocations, which are generated at the heterointerfaces in the GBL to relax strain. In this report, misfit dislocations inside the GBL of inverted metamorphic (IMM) single-junction InGaAs solar cells are directly observed by using two-photon excitation photoluminescence. A clear depth dependence of the dislocations inside the GBL can be confirmed. The results indicate that the strain relaxation processes in solar cells with high open-circuit voltages are distinctly different from those in solar cells with low open-circuit voltages.
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Fukuyama A., Tategami S., Takauchi K., Matsuda N., Nakamura T., Suzuki H., Nishioka K., Ikari T.
2018 IEEE 7th World Conference on Photovoltaic Energy Conversion, WCPEC 2018 - A Joint Conference of 45th IEEE PVSC, 28th PVSEC and 34th EU PVSEC 1792 - 1795 2018年11月
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：2018 IEEE 7th World Conference on Photovoltaic Energy Conversion, WCPEC 2018 - A Joint Conference of 45th IEEE PVSC, 28th PVSEC and 34th EU PVSEC
© 2018 IEEE. Hall mobility measurements of {n}- and p-type Si substrate under the concentrated sunlight irradiation were carried out to discuss the effect of large amount of carrier generation. The Hall mobility decreased Linearly with increasing the sunlight concentration. It was also found that these decrease could prevent by using a sample with high doping concentration. From the comparison with the calculation, we concluded that the reduction of Hall mobility was due to increase of the photo-generated carriers (both hole and electron). Calculation of Hall mobility as a function of impurity doping concentration demonstrated that a suitable doping concentration for solar cell use was considered to be 10{16}\mathrm {c}\mathrm {m}{-3} in both {n}- and p-type Si substrate from viewpoint of Hall mobility under 16-suns concentrated irradiation.
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Suzuki Hidetoshi, Sasaki Takuo, Takahasi Masamitu, Ohshita Yoshio, Kojima Nobuaki, Kamiya Itaru, Fukuyama Atsuhiko, Ikari Tetsuo, Yamaguchi Masafumi
Jpn. J. Appl. Phys. 56 ( 8 ) 2017年7月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Institute of Physics
The effect of substrate orientation on strain relaxation mechanisms of an InGaAs layer grown on vicinal GaAs substrates was investigated by in situ X-ray diffraction (XRD). The crystallographic tilt and indium segregation in the InGaAs layer were altered depending on the miscut direction and angle. In the case of the substrate tilted 6° toward the [110] direction, one type of misfit dislocations was formed preferentially rather than other types, especially in the rapid relaxation phase. While in the case of the substrate tilted 6° toward the [Formula: see text] direction, no anisotropies during relaxation were observed. The present finding indicates that the appropriate use of vicinal substrates may lead to a novel method of improving the crystal quality of heterolayers.
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Fukuyama Atsuhiko, Matsuochi Kouki, Nakamura Tsubasa, Takeda Hideaki, Toprasertpong Kasidit, Sugiyama Masakazu, Nakano Yoshiaki, Suzuki Hidetoshi, Ikari Tetsuo
Jpn. J. Appl. Phys. 56 ( 8 ) 2017年7月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Institute of Physics
To improve the superlattice (SL) solar cell performance, we carried out an accurate estimation of transition energies and miniband widths and focused on understanding of the optical properties of the SL structure using piezoelectric photothermal (PPT), photoreflectance (PR), and photoluminescence (PL) methods. Solar cell structure samples with different barrier thicknesses from 2.0 to 7.8 nm in quantum wells were prepared. From the PR and theoretical calculation, the formation of a miniband was confirmed. The PL peak showed a redshift and a decrease in signal intensity with decreasing barrier thickness, which were explained by carrier separation as a consequence of electron transportation through the miniband without recombination. The PPT signal intensities of the SL were still large even for the 2.0-nm-barrier-thickness sample. It is conceivable that the multiple-phonon emission during carrier transport through the miniband was detected. The usefulness of multidimensional investigation by using the above three methods is clearly demonstrated.
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Material conversion of GaAs nanowires 査読あり
Nishioka K., Suzuki H., Sakai K., Ishikawa F.
Physica Status Solidi (B) Basic Research 254 ( 2 ) 2017年2月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Physica Status Solidi (B) Basic Research
© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 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.