Article
Chemistry, Physical
Tao Zhang, Yifan Li, Yachao Zhang, Qian Feng, Jing Ning, Chunfu Zhang, Jincheng Zhang, Yue Hao
Summary: Beta-Ga2O3 films were grown on epi-GaN/sapphire substrates at different temperatures by low pressure MOCVD. The crystal structure, surface morphology, and element chemical state were influenced by temperature. Higher temperature led to improved crystal quality and surface morphology, as confirmed by XRD, AFM, and SEM analyses.
JOURNAL OF ALLOYS AND COMPOUNDS
(2021)
Article
Physics, Applied
Zhenni Yang, Xiangyu Xu, Yan Wang, Siliang Kuang, Duanyang Chen, Hongji Qi, K. H. L. Zhang
Summary: Si-doped beta-Ga2O3 thin films grown on vicinal a-Al2O3 (0001) substrates exhibit high electrical conductivity and deep ultraviolet (DUV) transparency, making them promising candidates for transparent electrodes. The use of miscut Al2O3 substrates promotes improved crystal quality and electrical properties. The Si-doped films achieved a high conductivity of 37 S cm(-1) and average DUV transparency of 85% on a 6 degrees miscut substrate. The films also exhibit low work function, making them suitable for efficient electron injection in DUV optoelectronic devices.
APPLIED PHYSICS LETTERS
(2023)
Article
Nanoscience & Nanotechnology
A. F. M. Anhar Uddin Bhuiyan, Zixuan Feng, Hsien-Lien Huang, Lingyu Meng, Jinwoo Hwang, Hongping Zhao
Summary: Single alpha-phase (AlxGa1-x)(2)O-3 thin films were successfully grown on m-plane sapphire substrates via metalorganic chemical vapor deposition, demonstrating high quality and uniformity. The influence of growth parameters on film properties was further investigated. X-ray photoelectron spectroscopy was employed to characterize the aluminum content and bandgaps, with the band alignment at heterojunctions also studied.
Article
Physics, Applied
Alexander Polyakov, Vladimir Nikolaev, Sergey Stepanov, Alexei Almaev, Alexei Pechnikov, Eugene Yakimov, Bogdan O. Kushnarev, Ivan Shchemerov, Mikhail Scheglov, Alexey Chernykh, Anton Vasilev, Anastasia Kochkova, Lyubov Guzilova, Stephen J. Pearton
Summary: The electrical and structural properties of alpha-Ga2O3 grown by HVPE are significantly influenced by the sapphire substrate orientation, and the use of alpha-Cr2O3 buffers has three major effects on it.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2022)
Article
Optics
Anoop Kumar Singh, Chao-Chun Yen, Kai-Ping Chang, Dong-Sing Wuu
Summary: This work discusses the growth, composition, and photoluminescence properties of Zn-doped Ga2O3 (ZnGaO) films. By doping Zn in ll-Ga2O3, the n-type conductivity of ll-Ga2O3 can be modulated to p-type. ZnGaO films with varying Zn contents were deposited on sapphire substrates, and X-ray analysis confirmed the stability of Zn dopant up to 8.62% in ZnGaO films. X-ray photoelectron spectroscopy revealed the increasing Zn content in ZnGaO films. The inclusion of Zn dopant in Ga2O3 films led to a shift in the peak emission wavelength of ll-Ga2O3 in the photoluminescence spectra, indicating the formation of more defect states and inducing green luminescence. The positive Hall coefficient of ZnGaO films verifies their p-type nature.
JOURNAL OF LUMINESCENCE
(2023)
Article
Materials Science, Multidisciplinary
Tyler Stabile, Yize Stephanie Li
Summary: This study investigates the deposition of strained alpha-Sn thin films on highly lattice-mismatched Ge (100) substrates by physical vapor deposition, using different cleaning methods. The results show that the morphology of thin films is significantly influenced by the cleaning method. It is demonstrated that the alpha-Sn thin films deposited on Ge substrates exhibit n-type electrical properties and may hold potential for advanced electronics and photonics applications.
MATERIALS TODAY ADVANCES
(2021)
Article
Engineering, Electrical & Electronic
Soo Hyeon Kim, Mino Yang, Hae-Yong Lee, Jong-Soon Choi, Hyun Uk Lee, Un Jeong Kim, Moonsang Lee
Summary: This study investigates the structural characterization of HVPE alpha-Ga2O3 materials via alkali KOH solution etching, revealing triangular-shaped etch pits caused by the propagation of threading dislocations. The activation energy of the etch rate for the materials, etch pit, and surface roughness after wet chemical treatment have been examined, providing insights into the structural behavior of alpha-Ga2O3 crystals during wet chemical etching.
MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING
(2021)
Article
Physics, Applied
Alexander Polyakov, Vladimir Nikolaev, Sergey Stepanov, Alexei Almaev, Alexei Pechnikov, Eugene Yakimov, Bogdan O. Kushnarev, Ivan Shchemerov, Mikhail Scheglov, Alexey Chernykh, Anton Vasilev, Anastasia Kochkova, Stephen J. Pearton
Summary: This study reports on the growth and electrical properties of alpha-Ga2O3 films grown on alpha-Cr2O3 buffers using halide vapor phase epitaxy. The experimental results showed p-type conductivity of the buffers and low donor ionization energies in Sn-doped alpha-Ga2O3 films prepared on these buffers.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Chemistry, Multidisciplinary
Jinshan Wei, Yuzhe Bu, Qinglin Sai, Hongji Qi, Jingbo Li, Huaimin Gu
Summary: In order to improve the n-type conductivity of single-crystal substrates, Sn element was intentionally added into β-Ga2O3 crystals as n-type dopants. However, it was found that the color of β-Ga2O3 crystal changed significantly after high-temperature remelting in the edge-defined film-fed growth (EFG) method. The carrier concentration in the colorless region was lower than that in the blue region, leading to a decrease in electrical conductivity after high-temperature remelting of Sn-doped β-Ga2O3.
Article
Engineering, Electrical & Electronic
Amit Kumar Singh, Saurabh Yadav, P. K. Kulriya, Y. S. Katharria
Summary: In this study, the annealing effects of sapphire substrate on beta-Ga2O3 thin films were investigated. The results showed that annealing improved the crystalline quality of the thin films and confirmed the presence of Ga-O bonds. The annealing temperature of the sapphire substrate influenced the film quality and the diffusion of aluminum atoms.
JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS
(2022)
Article
Crystallography
Ta-Shun Chou, Saud Bin Anooz, Raimund Grueneberg, Natasha Dropka, Wolfram Miller, Thi Thuy Vi Tran, Jana Rehm, Martin Albrecht, Andreas Popp
Summary: This study demonstrates the use of Random Forest, a machine learning approach, for predicting the growth rate of beta-Ga2O3 in metal-organic vapor phase epitaxy (MOVPE) by analyzing its growth process on sapphire. The proposed model can effectively evaluate the complex non-linear dependencies among growth parameters and optimize them to achieve the optimal growth rate. It achieves a high predictive power with a coefficient of determination (R-2) of 0.95 and 0.92 for the training and testing sets, respectively. The model's outcome is applicable to both homoepitaxial and heteroepitaxial processes, as well as different substrate orientations.
JOURNAL OF CRYSTAL GROWTH
(2022)
Article
Materials Science, Ceramics
Xiao Tang, Kuang-Hui Li, Che-Hao Liao, Jose Manuel Taboada Vasquez, Chuanju Wang, Na Xiao, Xiaohang Li
Summary: The study presents a novel CSD technique for depositing highly epitaxial indium and aluminum-doped Ga2O3 thin films, showing pure beta phase with good crystallization qualities. The incorporation of indium and aluminum shifts the crystallization of the thin films to lower and higher temperatures, respectively, and the bandgap of the sintered thin films can be tuned from 4.05 to 5.03 eV using mixed precursor solutions. Photodetectors based on the samples exhibit maximum photocurrents at different wavelengths, suggesting potential for producing high-quality bandgap tunable deep ultraviolet photoelectrical and high-power devices.
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
(2022)
Article
Nanoscience & Nanotechnology
Tanja Jawinski, Chris Sturm, Roland Clausing, Heiko Kempa, Marius Grundmann, Roland Scheer, Holger von Wenckstern
Summary: In this study, indium sulfide (In2S3) thin films were deposited on glass and sapphire substrates by physical co-evaporation. The structural properties of the films were optimized by varying the deposition parameters. The sample grown epitaxially on an α-sapphire substrate exhibited the smoothest surface and highest crystallinity. The optical absorption properties were found to be independent of the deposition parameters and substrate material. Weak and strong absorption onsets were observed at 1.7 eV and 2.5 eV, respectively, which were attributed to direct band-band transitions at 2.1 eV and 2.7 eV. The electrical characterization revealed photovoltaic activity but low performance due to non-ideal heterojunction properties. A strong and persistent photoconductivity was also observed, resulting in a time-dependent dark resistivity after light exposure.
Article
Materials Science, Ceramics
Su Yeon Cha, Dongwoo Kim, Hojoon Lim, Bongjin Simon Mun, Do Young Noh, Hyon Chol Kang
Summary: The study focused on the synthesis and characterization of non-stoichiometric Ga2O3-x thin films deposited on sapphire substrates using radio-frequency powder sputtering. The thin films were found to have electronic states mainly consisting of Ga3+ and Ga1+, exhibiting semiconductor electrical characteristics.
CERAMICS INTERNATIONAL
(2021)
Article
Materials Science, Multidisciplinary
Wanli Xu, Jiacheng Shi, Yuewen Li, Xiangqian Xiu, Shan Ding, Zili Xie, Tao Tao, Peng Chen, Bin Liu, Rong Zhang, Youdou Zheng
Summary: In this study, the effects of off-angled sapphire substrates on the surface morphologies and crystal quality of heteroepitaxial beta-Ga2O3 films were systematically investigated. The results showed that the films grown on substrates with an off-angle of around 7 degrees exhibited a flatter surface morphology and better crystal quality, compared to films grown on (0 0 0 1) sapphire. These findings could be beneficial for the heteroepitaxy of high-quality Ga2O3 films with smooth surfaces.
Article
Physics, Applied
Kentaro Kaneko, Shizuo Fujita, Toshimi Hitora
JAPANESE JOURNAL OF APPLIED PHYSICS
(2018)
Article
Physics, Applied
Takayuki Uchida, Riena Jinno, Shu Takemoto, Kentaro Kaneko, Shizuo Fujita
JAPANESE JOURNAL OF APPLIED PHYSICS
(2018)
Article
Engineering, Electrical & Electronic
Kentaro Kaneko, Keiichi Tsumura, Kyohei Ishii, Takayoshi Onuma, Tohru Honda, Shizuo Fujita
JOURNAL OF ELECTRONIC MATERIALS
(2018)
Article
Physics, Condensed Matter
Riena Jinno, Takayuki Uchida, Kentaro Kaneko, Shizuo Fujita
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS
(2018)
Article
Physics, Applied
Kyohei Ishii, Mizuki Ono, Kentaro Kaneko, Takeyoshi Onuma, Tohru Honda, Shizuo Fujita
APPLIED PHYSICS EXPRESS
(2019)
Article
Physics, Applied
M. Ono, K. Ishii, K. Kaneko, T. Yamaguchi, T. Honda, S. Fujita, T. Onuma
JOURNAL OF APPLIED PHYSICS
(2019)
Article
Physics, Applied
Riena Jinno, Nobuhiro Yoshimura, Kentaro Kaneko, Shizuo Fujita
JAPANESE JOURNAL OF APPLIED PHYSICS
(2019)
Article
Physics, Applied
Tomohiro Yamaguchi, Subaru Takahashi, Takanori Kiguchi, Atsushi Sekiguchi, Kentaro Kaneko, Shizuo Fujita, Hiroki Nagai, Mitsunobu Sato, Takeyoshi Onuma, Tohru Honda
APPLIED PHYSICS EXPRESS
(2020)
Article
Physics, Applied
Riena Jinno, Kentaro Kaneko, Shizuo Fujita
Summary: The thermal stability of alpha-(AlxGa1-x)(2)O-3 films grown on c-plane sapphire substrates was explored through annealing at different temperatures. It was found that lower Al composition led to phase transformation to the most stable phase for Ga2O3, while higher Al composition improved thermal stability. Films with x = 0.45 maintained the corundum structure after annealing at 950 degrees C, while layers with Al contents above 0.6 remained stable and did not undergo phase transformation at 1100 degrees C.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2021)
Article
Physics, Applied
Kentaro Kaneko, Yasuhisa Masuda, Shin-ichi Kan, Isao Takahashi, Yuji Kato, Takashi Shinohe, Shizuo Fujita
Summary: Ultra-wide bandgap p-type alpha-(Ir,Ga)(2)O-3 films were achieved through unintentional or Mg doping, showing potential for high-quality pn heterojunction formation with n-type alpha-Ga2O3 due to their similar crystal structures and good lattice matching. Initial testing of a pn junction diode composed of these materials demonstrated promising performance.
APPLIED PHYSICS LETTERS
(2021)
Article
Physics, Condensed Matter
Hitoshi Takane, Kentaro Kaneko, Takashi Shinohe, Shizuo Fujita
Summary: Deep traps in n-type alpha-Ga2O3 grown by mist chemical vapor deposition are analyzed, revealing trap levels at approximately 2.0 eV, 2.5 eV, and 3.2 eV. The concentrations of these traps are lower than previously reported for alpha-Ga2O3, and a large Frank-Condon shift indicates a high degree of lattice coupling in the midgap state of alpha-Ga2O3.
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS
(2021)
Article
Physics, Applied
Hitoshi Takane, Kentaro Kaneko, Yuichi Ota, Shizuo Fujita
Summary: The study compared the growth characteristics of α-Ga2O3 under different growth methods and revealed the unique mechanism of mist CVD-grown α-Ga2O3.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2021)
Article
Nanoscience & Nanotechnology
Riena Jinno, Kentaro Kaneko, Shizuo Fujita
Proceedings Paper
Engineering, Electrical & Electronic
K. Kudo, K. Ishii, M. Ono, Y. Fujiwara, K. Kaneko, T. Yamaguchi, T. Honda, S. Fujita, T. Onuma
2019 COMPOUND SEMICONDUCTOR WEEK (CSW)
(2019)
Article
Materials Science, Multidisciplinary
Takayuki Uchida, Kentaro Kaneko, Shizuo Fujita
