Article
Physics, Applied
Takayoshi Oshima, Yuichi Oshima
Summary: In this study, SiO2-masked (001) beta-Ga2O3 substrates were dry etched in HCl gas flow at a high temperature without plasma excitation. The etching selectively formed holes or trenches with inner sidewalls of (100) and/or {310} facets, which are planes of lowest surface energy density and oxygen-close-packed slip planes, respectively. The (100) faceted sidewalls were flat and close to the substrate surface normal. This dry etching method shows promise for fabricating plasma-damage-free trenches and fins for beta-Ga2O3-based power devices.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
Sayleap Sdoeung, Kohei Sasaki, Katsumi Kawasaki, Jun Hirabayashi, Akito Kuramata, Toshiyuki Oishi, Makoto Kasu
Summary: Line-shaped defects were observed in halide vapor-phase epitaxial (001) beta-Ga2O3 SBDs, and these defects were found to be related to the reverse leakage current. Atomic force microscopy observation and simulation results showed that the formation of line-shaped defects originated from a dislocation network near the crystal surface.
APPLIED PHYSICS LETTERS
(2022)
Article
Materials Science, Coatings & Films
Dinusha Herath Mudiyanselage, Dawei Wang, Houqiang Fu
Summary: In this study, ultrawide bandgap beta-(AlxGa1-x)(2)O-3 vertical Schottky barrier diodes on (010) beta-Ga2O3 substrates were fabricated and demonstrated. The fabricated devices exhibited excellent rectification properties with a high on/off ratio, a low turn-on voltage, and a low on-resistance. The leakage mechanisms of the devices were analyzed and it was found that Poole-Frenkel emission and trap-assisted tunneling were the main mechanisms at high and low temperatures, respectively. This work provides an important reference for the future development of ultrawide bandgap beta-(AlxGa1-x)(2)O-3 power electronics, RF electronics, and ultraviolet photonics.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2023)
Article
Physics, Applied
Sudipto Saha, Lingyu Meng, Zixuan Feng, A. F. M. Anhar Uddin Bhuiyan, Hongping Zhao, Uttam Singisetti
Summary: This paper presents a systematic study on the Schottky diodes fabricated on Si-doped homoepitaxial beta-Ga2O3 thin films grown on different substrates by LPCVD. The results show that higher temperature growth leads to the highest growth rate and the characteristics of the diodes are analyzed and studied.
APPLIED PHYSICS LETTERS
(2022)
Article
Engineering, Electrical & Electronic
Shaozhong Yue, Xuefeng Zheng, Yuehua Hong, Xiangyu Zhang, Fang Zhang, Yingzhe Wang, Xiaohua Ma, Yue Hao
Summary: This study investigates the effect of neutron irradiation on the electrical performance of the beta-Ga2O3 Schottky barrier diode (SBD) device. The results show that after neutron irradiation, there is a decrease in forward current density (J(F)), reduction in reverse current density (J(R)), and increase in breakdown voltage (V-br) based on current-voltage (I-V) measurements. The density of interface states slightly increases, and there is an increase in trap activation energy after neutron irradiation according to frequency-dependent conductance technique. The carrier concentration across the Ga2O3 drift layer decreases after neutron irradiation based on capacitance-voltage (C-V) measurements.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Article
Physics, Applied
Prabhans Tiwari, Jayeeta Biswas, Chandan Joishi, Saurabh Lodha
Summary: By utilizing Nb2O5 as the high-k dielectric insulator, the MIS diode demonstrated more efficient electric field management and enhanced breakdown characteristics compared to the beta-Ga2O3 Schottky diode, resulting in a 3-fold increase in the power figure of merit with a slight trade-off in specific on-resistance. Analysis of energy band line-up and current transport mechanisms were also presented using analytical modeling and computer-aided design simulations.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Crystallography
Maolin Zhang, Zeng Liu, Lili Yang, Jiafei Yao, Jing Chen, Jun Zhang, Wei Wei, Yufeng Guo, Weihua Tang
Summary: This review article summarizes recent advances in the experimental and theoretical research on β-Ga2O3-based power devices, providing comprehensive guidance for further development by discussing the operating mechanisms and obstacles to be addressed.
Article
Physics, Applied
Takaya Sugiura, Nobuhiko Nakano
Summary: This study focuses on the breakdown operations modeling of gallium oxide (Ga2O3), proposing models that consider both soft and hard breakdown phenomena. The impact ionization model of β-Ga2O3 in <001> orientation is improved, reproducing hard breakdown operations. A barrier lowering model is also determined for reproducing soft breakdown operations. These modeling outcomes are crucial for predicting reverse-biased operations and further technological development and applications of Ga2O3.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Physics, Applied
Z. P. Wang, H. H. Gong, X. X. Yu, T. C. Hu, X. L. Ji, F. -F. Ren, S. L. Gu, Y. D. Zheng, R. Zhang, J. D. Ye
Summary: This study investigates the relationship between trap inhomogeneity within beta-Ga2O3 and the conversion of Shockley-Read-Hall (SRH) recombination in NiO/beta-Ga2O3 p(+)-n heterojunction diodes. The analysis identifies near-surface traps E2 and E3, as well as bulk traps E2*, and shows that carrier transport under forward bias is mainly governed by trap-assisted tunneling through the E3 traps with high recombination rates. The elimination of near-surface traps leads to improved diode performance and enables the development of high-performance power rectifiers.
APPLIED PHYSICS LETTERS
(2023)
Article
Engineering, Electrical & Electronic
Shaozhong Yue, Xuefeng Zheng, Yuehua Hong, Xiangyu Zhang, Fang Zhang, Yingzhe Wang, Ling Lv, Yanrong Cao, Xiaohua Ma, Yue Hao
Summary: This article studies the effect of hydrogen on b-gallium oxide (Ga2O3) (001) Schottky barrier diode (SBD) device for the first time. It is found that the electrical performance of the beta-Ga2O3 SBDs changed significantly after hydrogen treatment, with a decrease in turn-on voltage (V-on) by 0.3 V and an increase in forward (JF) current density by 28%. Frequency-dependent conductance technique reveals that the time constants decreased from 0.09-0.3 to 0.06-0.09 mu s after hydrogen treatment. The density of interface states and trap activation energy also decreased after hydrogen treatment. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) shows an increased density of hydrogen at the Pt/Ga2O3 interface for the device with hydrogen treatment. The effect of hydrogen on Pt/Au beta-Ga2O3 SBDs is mainly attributed to the passivation of traps by hydrogen atoms near the Pt/Ga2O3 interface.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Article
Physics, Applied
G. Alfieri, A. Mihaila, P. Godignon, J. B. Varley, L. Vines
Summary: This study investigates the effects of chlorine-based gases on the electronic properties of beta-Ga2O3. The experimental and theoretical research reveals the formation of four traps in the energy range below the conduction band edge, with two traps appearing only after treatment with BCl3/Ar plasma. The findings provide insight into the potential impact of Cl-plasma treatment on the electronic properties of beta-Ga2O3.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Physics, Multidisciplinary
Pei-Pei Ma, Jun Zheng, Ya-Bao Zhang, Xiang-Quan Liu, Zhi Liu, Yu-Hua Zuo, Chun-Lai Xue, Bu-Wen Cheng
Summary: Lateral beta-Ga2O3 Schottky barrier diodes with L-shaped electrodes were fabricated on an unintentionally doped (-201) n-type beta-Ga2O3 single crystal substrate. By introducing sidewall electrodes, the diode exhibited high current density and low specific on-resistance. Temperature-dependent performance analysis showed promising results, indicating the great potential of lateral beta-Ga2O3 SBDs for future power electronic applications.
Article
Chemistry, Multidisciplinary
Lingyu Meng, Zixuan Feng, A. F. M. Anhar Uddin Bhuiyan, Hongping Zhao
Summary: In this study, high-quality Ga2O3 thin films were successfully grown with fast growth rates using metalorganic chemical vapor deposition (MOCVD). Key growth parameters and the flow rate of n-type dopant silane were adjusted to achieve high crystalline quality, high mobility, and low compensation level. These results are crucial for the development of high power electronic device technology.
CRYSTAL GROWTH & DESIGN
(2022)
Article
Physics, Applied
Z. Dela Cruz, C. Hou, R. F. Martinez-Gazoni, R. J. Reeves, M. W. Allen
Summary: The performance of beta-Ga2O3 Schottky contacts (SCs) fabricated using amorphous, intentionally oxidized platinum-iridium alloys was investigated. The study found that Pt0.5Ir0.5Ox SCs had the highest Schottky barriers on all beta-Ga2O3 crystal faces, providing better contacts and lower reverse leakage currents. All PtyIr(1-y)Ox SCs on ( 2 over bar 01) beta-Ga2O3 showed excellent high-temperature performance.
APPLIED PHYSICS LETTERS
(2022)
Article
Engineering, Electrical & Electronic
Ailing Pan, Yingzhe Wang, Xuefeng Zheng, Yuehua Hong, Fang Zhang, Xiangyu Zhang, Ling Lv, Yanrong Cao, Xiaohua Ma, Yue Hao
Summary: The transformation of current transport mechanism and defect behavior in beta-gallium oxide Schottky barrier diodes (SBDs) under constant forward bias stress is investigated in this study. It is found that the predominant transport mechanism for both forward and reverse leakage current changes from thermionic emission to trap-assisted tunneling after stress. The generation of shallow-level defects and ionization of newly generated shallow donors contribute to the enhancement of trap-assisted tunneling.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Article
Physics, Applied
Ritsuko Sato, Yasuo Chiba, Masayuki Chikamatsu, Yuji Yoshida, Tetsuya Taima, Makoto Kasu, Atsushi Masuda
JAPANESE JOURNAL OF APPLIED PHYSICS
(2020)
Article
Physics, Applied
Yuichi Oshima, Katsuaki Kawara, Takayoshi Oshima, Mitsuru Okigawa, Takashi Shinohe
JAPANESE JOURNAL OF APPLIED PHYSICS
(2020)
Article
Engineering, Electrical & Electronic
Yuichi Oshima, Katsuaki Kawara, Takayoshi Oshima, Mitsuru Okigawa, Takashi Shinohe
SEMICONDUCTOR SCIENCE AND TECHNOLOGY
(2020)
Article
Physics, Applied
Katsuaki Kawara, Takayoshi Oshima, Mitsuru Okigawa, Takashi Shinohe
APPLIED PHYSICS EXPRESS
(2020)
Article
Physics, Applied
Yuichi Oshima, Katsuaki Kawara, Takayoshi Oshima, Takashi Shinohe
JAPANESE JOURNAL OF APPLIED PHYSICS
(2020)
Article
Physics, Applied
Niloy Chandra Saha, Kazutoshi Takahashi, Masaki Imamura, Makoto Kasu
JOURNAL OF APPLIED PHYSICS
(2020)
Article
Physics, Applied
Tamotsu Okamoto, Tomoya Igari, Takahiro Fukui, Ryuto Tozawa, Yasuhito Gotoh, Nobuhiro Sato, Yasuki Okuno, Tomohiro Kobayashi, Mitsuru Imaizumi, Masafumi Akiyoshi
Summary: In this study, a compact and radiation-tolerant radiation dosimeter without bias voltage application using CdTe solar cells was proposed for severe radiation environment near a nuclear reactor pressure vessel. The CdTe solar cells showed sufficient tolerance against gamma-ray exposure up to 3 MGy and linearly increased current density with increasing gamma-ray intensity. By stacking and parallel connecting CdTe solar cells, gamma-ray sensitivity was successfully improved, enabling high responsivity and low noise detection even under high flux neutron environments.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2021)
Article
Chemistry, Multidisciplinary
Jianbo Liang, Ayaka Kobayashi, Yasuo Shimizu, Yutaka Ohno, Seong-Woo Kim, Koji Koyama, Makoto Kasu, Yasuyoshi Nagai, Naoteru Shigekawa
Summary: The direct integration of GaN and diamond for high-power devices faces challenges due to mismatch in lattice and thermal-expansion coefficients. A successful fabrication of GaN/diamond heterointerface was achieved using a surface activated bonding method at room temperature. An intermediate layer composed of amorphous carbon and diamond is formed at the interface, with Ga and N atoms diffusing during the bonding process and transitioning to diamond after annealing.
ADVANCED MATERIALS
(2021)
Article
Physics, Applied
Sayleap Sdoeung, Kohei Sasaki, Katsumi Kawasaki, Jun Hirabayashi, Akito Kuramata, Makoto Kasu
Summary: The surface defects induced by probe attachment play a crucial role in causing reverse leakage current in β-Ga2O3 SBDs, which is essential for the commercialization of power devices.
APPLIED PHYSICS LETTERS
(2022)
Article
Chemistry, Multidisciplinary
Laura E. Ratcliff, Takayoshi Oshima, Felix Nippert, Benjamin M. Janzen, Elias Kluth, Rudiger Goldhahn, Martin Feneberg, Piero Mazzolini, Oliver Bierwagen, Charlotte Wouters, Musbah Nofal, Martin Albrecht, Jack E. N. Swallow, Leanne A. H. Jones, Pardeep K. Thakur, Tien-Lin Lee, Curran Kalha, Christoph Schlueter, Tim D. Veal, Joel B. Varley, Markus R. Wagner, Anna Regoutz
Summary: Ga2O3 and its polymorphs have great potential for electronic structure engineering. In this study, a robust atomistic model of gamma-Ga2O3 is developed using density functional theory and machine-learning approach, which is validated by experimental results. This work is of significant importance for understanding the electronic structure of complex, disordered oxides.
ADVANCED MATERIALS
(2022)
Article
Physics, Applied
Takayoshi Oshima, Yuichi Oshima
Summary: Selective area growth of beta-Ga2O3 was demonstrated by HCl-based halide vapor phase epitaxy on SiO2-masked (001) and (010) beta-Ga2O3 substrates. High-aspect-ratio structures with (100) sidewall facets were observed for stripe windows along [010] and [001] directions on the respective substrates. These structures can be applied to trenches and fins for beta-Ga2O3-based power devices.
APPLIED PHYSICS EXPRESS
(2022)
Article
Physics, Applied
Takayoshi Oshima
Summary: In this study, a patterned metal on a beta-Ga2O3 substrate surface was used as an embedded photomask to demonstrate the applicability of backside-exposure lithography to beta-Ga2O3 substrates. Self-aligned photoresist patterning, lift-off, and etching processes were demonstrated for an AZ5214E photoresist in both the positive and negative processing modes. The findings suggest that backside-exposure photolithography is a promising fabrication approach for future beta-Ga2O3-based devices.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
Hitoshi Takane, Takayoshi Oshima, Katsuhisa Tanaka, Kentaro Kaneko
Summary: Selective-area growth of r-SnO2 was achieved on a SiO2-masked r-TiO2 (110) substrate. The heteroepitaxy process led to the growth of islands with {100}-, {110}-, and {011}-faceted sidewalls, which matched the equilibrium shape of the rutile structure. Coalescence of the islands formed a flat (110) top surface on the striped window, followed by lateral overgrowth. Cross-sectional transmission-electron-microscopy observation revealed that misfit dislocations propagated perpendicular to the facet planes due to the image force effect, and the dislocation density decreased significantly in the wing regions.
APPLIED PHYSICS EXPRESS
(2023)
Article
Physics, Applied
Takayoshi Oshima, Yuichi Oshima
Summary: We have demonstrated the effectiveness of plasma-free HCl gas etching for fabricating high-aspect-ratio fins/trenches on a SiO2-masked (010) beta-Ga2O3 substrate. The etching process resulted in the formation of holes or trenches with etching-resistant (100)- and ((1) over bar 01)-faceted sidewalls. By etching in the striped windows along [001], we achieved fins and trenches with flat (100)-faceted vertical sidewalls and slightly rough {310}-faceted inclined bottom corners. The vertical-to-horizontal etching ratio was as high as about 11-14. Our findings suggest that HCl etching is a promising method for such fabrication without plasma damage.
APPLIED PHYSICS EXPRESS
(2023)
Article
Physics, Applied
Takayoshi Oshima, Yuichi Oshima
Summary: In this study, SiO2-masked (001) beta-Ga2O3 substrates were dry etched in HCl gas flow at a high temperature without plasma excitation. The etching selectively formed holes or trenches with inner sidewalls of (100) and/or {310} facets, which are planes of lowest surface energy density and oxygen-close-packed slip planes, respectively. The (100) faceted sidewalls were flat and close to the substrate surface normal. This dry etching method shows promise for fabricating plasma-damage-free trenches and fins for beta-Ga2O3-based power devices.
APPLIED PHYSICS LETTERS
(2023)
