Article
Nanoscience & Nanotechnology
Hemant Ghadi, Joe F. McGlone, Evan Cornuelle, Zixuan Feng, Yuxuan Zhang, Lingyu Meng, Hongping Zhao, Aaron R. Arehart, Steven A. Ringel
Summary: This study evaluates the defect state distribution in beta phase gallium oxide (beta-Ga2O3) grown by low-pressure chemical vapor deposition (LPCVD). The presence of a previously unreported defect state and other known defect states were observed. The trap concentration in the LPCVD-grown material was lower compared to materials grown by other methods, and the distribution of the defect states showed little dependence on the SiCl4 flow rate and doping concentration. These findings indicate that LPCVD-grown beta-Ga2O3 has great potential for producing thick, low-defect density, and high-quality layers for multi-kV device applications.
Article
Physics, Applied
Joe F. McGlone, Hemant Ghadi, Evan Cornuelle, Andrew Armstrong, George Burns, Zixuan Feng, A. F. M. Anhar Uddin Bhuiyan, Hongping Zhao, Aaron R. Arehart, Steven A. Ringel
Summary: The impact of 1.8 MeV proton irradiation on metalorganic chemical vapor deposition grown (010) beta-Ga2O3 Schottky diodes was studied. It was found that the Schottky barrier height and ideality factor were unaffected after a certain proton fluence. Carrier removal rate and defect states responsible for the observed carrier removal were analyzed. The comprehensive defect characterization can aid the modeling and design for radiation tolerant devices.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Condensed Matter
Kun Zhang, Zongwei Xu, Shengnan Zhang, Hong Wang, Hongjuan Cheng, Jianmin Hao, Jintong Wu, Fengzhou Fang
Summary: In this study, beta-Ga2O3 single crystals with different orientations and dopants are synthesized using the EFG method. The effects of doping on vibration modes frequencies are analyzed using Raman spectroscopy, while the emission characteristics in PL spectroscopy show different behavior based on the type of dopant used.
PHYSICA B-CONDENSED MATTER
(2021)
Article
Chemistry, Multidisciplinary
Pengkun Li, Yuzhe Bu, Duanyang Chen, Qinglin Sai, Hongji Qi
Summary: The presence of a crack along the seed of a beta-gallium oxide crystal grown using the EFG method has a significant impact on crystal slicing efficiency but minor effects on its structural, electronic, and optical properties. The crystal on the right side of the crack exhibits more defects caused by oxygen vacancies compared to the one on the left side.
Article
Nanoscience & Nanotechnology
Ymir K. Frodason, Patryk P. Krzyzaniak, Lasse Vines, Joel B. Varley, Chris G. Van de Walle, Klaus Magnus H. Johansen
Summary: The diffusion of the n-type dopant Sn in beta-Ga2O3 was studied using secondary-ion mass spectrometry combined with hybrid functional calculations. It was found that Ga vacancies mediate the migration of Sn through the formation and dissociation of intermittent mobile VGaSnGa complexes. The migration barrier for the VGaSnGa complex was determined to be 3.0 +/- 0.4 eV, consistent with theoretical predictions using the nudged elastic band method.
Article
Nanoscience & Nanotechnology
Fikadu Alema, George Seryogin, Alexei Osinsky, Andrei Osinsky
Summary: Ge doping in Ga2O3 was studied using MOCVD epitaxy, where factors influencing the incorporation efficiency of Ge were explored. Results showed that Ge incorporation was strongly dependent on parameters such as GeH4/N-2 flow rate, substrate temperature, and VI/III ratio. The study also found that the choice of Ga precursor and MOCVD reactor geometry played a significant role in the Ge doping process, highlighting challenges in achieving controllable Ge doping for n-type conductivity.
Article
Physics, Applied
Ta-Shun Chou, Saud Bin Anooz, Raimund Grueneberg, Natasha Dropka, Jana Rehm, Thi Thuy Vi Tran, Klaus Irmscher, Palvan Seyidov, Wolfram Miller, Zbigniew Galazka, Martin Albrecht, Andreas Popp
Summary: (English Summary:)
This study proposes a Langmuir adsorption model for the Si incorporation mechanism into (100) beta-Ga2O3 thin films grown by metalorganic vapor-phase epitaxy, based on the competitive surface adsorption process between Si and Ga atoms. The model describes the major features of the doping process and shows a growth rate-dependent doping behavior, which is experimentally validated and further generalized to different growth conditions and substrate orientations.
APPLIED PHYSICS LETTERS
(2022)
Article
Physics, Applied
Suman Bhandari, M. E. Zvanut
Summary: Fe-doped beta-Ga2O3 crystals grown by Czochralski and floating zone methods were studied, revealing different optical transitions associated with Fe. EPR tests showed Fe-related transitions near 1-2 eV in both Cz and FZ samples, another at 2.5 eV unique to Cz Ga2O3, and a third near 3 eV in FZ material.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Physics, Applied
Ken Goto, Hisashi Murakami, Akito Kuramata, Shigenobu Yamakoshi, Masataka Higashiwaki, Yoshinao Kumagai
Summary: The influence of substrate orientation on the homoepitaxial growth of beta-gallium oxide was investigated. It was found that the growth rate increased near the (001) substrate, but sharply decreased from (001) to (010) with triangular pits formed on the grown layer. The pits were found to originate from dislocations propagating in the substrate at an angle of 60° with respect to the (001) plane. A pit-free homoepitaxial layer was achieved when the substrate orientation was around 60°.
APPLIED PHYSICS LETTERS
(2022)
Article
Physics, Applied
Sayleap Sdoeung, Kohei Sasaki, Satoshi Masuya, Katsumi Kawasaki, Jun Hirabayashi, Akito Kuramata, Makoto Kasu
Summary: Killer defects in beta-Gallium Oxide (beta-Ga2O3) Schottky barrier diodes, responsible for leakage current and breakdown, are mainly stacking faults in the halide vapor phase epitaxial (HVPE) (001) layer, including (111) and (1 1 1) stacking faults, and stacking faults formed by microparticles due to low gas flow rate during HVPE growth. These defects result in different levels of leakage current at -200V and are characterized by heart-shaped and bullet-shaped etch pits.
APPLIED PHYSICS LETTERS
(2021)
Article
Physics, Applied
Coralie Perrier, Aboulaye Traore, Toshimitsu Ito, Hitoshi Umezawa, Etienne Gheeraert, Philippe Ferrandis
Summary: We investigated beta-Ga2O3 Schottky barrier diodes grown on substrates using various characterization techniques and electrical measurements. Four electron trap levels were identified, with one near the surface and the others showing similarities to the literature. The surface trap was found to be linked to substrate polishing damage, while an energy band at the metal-semiconductor interface was also detected. These interface states and surface deep traps contributed to the degradation of diode performance.
APPLIED PHYSICS LETTERS
(2023)
Article
Materials Science, Coatings & Films
Jacqueline Cooke, Praneeth Ranga, Arkka Bhattacharyya, Xueling Cheng, Yunshan Wang, Sriram Krishnamoorthy, Michael A. Scarpulla, Berardi Sensale-Rodriguez
Summary: We report the discovery of a new type of structural defect in beta-Ga2O3 homoepitaxial thin films, which we call sympetalous defects. These defects consist of a line defect in the substrate combined with a multi-faceted inverted polycrystalline pyramid in the epitaxial film. Photoluminescence microscopy revealed polarization-dependent luminescence and circular dichroism at these defects. Understanding and controlling these defects is important for modifying film properties, affecting device yields, and influencing characterization experiments.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2023)
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
Nanoscience & Nanotechnology
Kathy Azizie, Felix V. E. Hensling, Cameron A. Gorsak, Yunjo Kim, Naomi A. Pieczulewski, Daniel M. Dryden, M. K. Indika Senevirathna, Selena Coye, Shun-Li Shang, Jacob Steele, Patrick Vogt, Nicholas A. Parker, Yorick A. Birkholzer, Jonathan P. McCandless, Debdeep Jena, Huili G. Xing, Zi-Kui Liu, Michael D. Williams, Andrew J. Green, Kelson Chabak, David A. Muller, Adam T. Neal, Shin Mou, Michael O. Thompson, Hari P. Nair, Darrell G. Schlom
Summary: We demonstrate the use of suboxide molecular-beam epitaxy (S-MBE) to successfully grow beta-Ga2O3 at a growth rate of approximately 1 μm/h with controlled silicon doping concentration. By directly supplying Ga2O to the growth surface, S-MBE bypasses the rate-limiting step in conventional MBE, resulting in high-quality films with smooth surfaces. The silicon-doped beta-Ga2O3 films grown by S-MBE show promising properties for metal-semiconductor field-effect transistors.
Article
Physics, Applied
Hirotaka Yamaguchi, Shinya Watanabe, Yu Yamaoka, Kimiyoshi Koshi, Akito Kuramata
Summary: The mechanical and dislocation properties of beta-Ga2O3 were investigated. Sharp cracks along the (100) and (001) planes were observed on the (010)-oriented substrate. The small Vickers hardness for the (010)-oriented substrate indicated that the (010) surface is fragile. Dislocation evolution on the (001) plane was also observed after heat treatment. These findings suggest that the (001) plane is a slip plane in this material.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2022)
Editorial Material
Physics, Applied
Takashi Itoh, Shigeya Naritsuka, Yasufumi Fujiwara, Mineo Hiramatsu, Makoto Kasu, Kazunori Koga, Hiroki Kondo, Koh Matsumoto, Osamu Nakatsuka, Kiichi Niitsu, Tomohiro Nozaki, Takayuki Ohta, Osamu Sakai, Hideki Sato, Tetsuya Takeuchi, Giichiro Uchida
JAPANESE JOURNAL OF APPLIED PHYSICS
(2017)
Review
Physics, Applied
Makoto Kasu
JAPANESE JOURNAL OF APPLIED PHYSICS
(2017)
Article
Materials Science, Multidisciplinary
A. Boussadi, A. Tallaire, M. Kasu, J. Barjon, J. Achard
DIAMOND AND RELATED MATERIALS
(2018)
Article
Materials Science, Multidisciplinary
Satoshi Masuya, Makoto Kasu
DIAMOND AND RELATED MATERIALS
(2018)
Article
Materials Science, Multidisciplinary
Niloy Chandra Saha, Makoto Kasu
DIAMOND AND RELATED MATERIALS
(2019)
Article
Materials Science, Multidisciplinary
Niloy Chandra Saha, Makoto Kasu
DIAMOND AND RELATED MATERIALS
(2019)
Article
Materials Science, Multidisciplinary
Jianbo Liang, Yan Zhou, Satoshi Masuya, Filip Gucmann, Manikant Singh, James Pomeroy, Seongwoo Kim, Martin Kuball, Makoto Kasu, Naoteru Shigekawa
DIAMOND AND RELATED MATERIALS
(2019)
Article
Physics, Applied
Ritsuko Sato, Yasuo Chiba, Masayuki Chikamatsu, Yuji Yoshida, Tetsuya Taima, Makoto Kasu, Atsushi Masuda
JAPANESE JOURNAL OF APPLIED PHYSICS
(2019)
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
Ritsuko Sato, Tetsuyuki Ishii, Sungwoo Choi, Yasuo Chiba, Makoto Kasu, Atsushi Masuda
JAPANESE JOURNAL OF APPLIED PHYSICS
(2019)
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
Physics, Applied
Takayoshi Oshima, Yuji Kato, Masaya Oda, Toshimi Hitora, Makoto Kasu
APPLIED PHYSICS EXPRESS
(2017)