Article
Materials Science, Multidisciplinary
Chao-Ching Chiang, Xinyi Xia, Jian-Sian Li, Fan Ren, S. J. Pearton
Summary: Patterning of NiO/Ga2O3 heterojunctions requires development of selective wet and dry etch processes. Wet etching of NiO using 1:4 HNO3:H2O solution showed measurable etch rates above 40 degrees C, with infinite selectivity over β-Ga2O3 below 55 degrees C. Dry etching using Cl-2/Ar plasma achieved etch rates up to 800 angstrom.min(-1), with maximum selectivities for β-Ga2O3.
ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY
(2022)
Article
Engineering, Electrical & Electronic
Rongrong Chen, Chongchong Zhao, Caina Luan, Jin Ma, Hongdi Xiao
Summary: In this study, beta-Ga2O3 films were grown on GaN substrates using metal organic chemical vapor deposition (MOCVD), and optimized through oxalic acid etching. The results showed that under appropriate etching conditions, the films exhibited the best crystal quality, and the porous structure of the substrate reduced crystal defects.
MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING
(2023)
Review
Chemistry, Multidisciplinary
Zhu Jin, Yingying Liu, Ning Xia, Xiangwei Guo, Zijian Hong, Hui Zhang, Deren Yang
Summary: This review article summarizes recent advances in wet etching of β-Ga2O3 substrates, aiming to comprehensively understand the etching behavior and mechanism. Wet etching is classified into conventional and unconventional types, each with key parameters controlling etching kinetics discussed and examples highlighted. The review intends to provide guidance on designing appropriate etching strategies for various purposes and applications.
Article
Materials Science, Ceramics
Badriyah Alhalaili, Ruxandra Vidu, Howard Mao, Olfa Kamoun, M. Saif Islam
Summary: The interest in using gallium oxide (Ga2O3) in semiconductor devices has increased due to its wide bandgap allowing device operation at high temperatures and high voltages. Photoelectrochemical etching of Ga2O3 introduces adjustable parameters to control the etching process, making it suitable for applications requiring complex patterning with high degrees of control compared to traditional etching methods. This method has the potential to produce nano-features at the required scale while causing minimal device degradation.
CERAMICS INTERNATIONAL
(2021)
Article
Chemistry, Multidisciplinary
Arpit Nandi, David Cherns, Indraneel Sanyal, Martin Kuball
Summary: Heteroepitaxial growth of beta-Ga2O3 on (001) diamond by MOCVD was achieved, and the epitaxial relationship and crystal structure were studied using TEM.
CRYSTAL GROWTH & DESIGN
(2023)
Article
Chemistry, Physical
Ning Xia, Yingying Liu, Dan Wu, Lei Li, Keke Ma, Jiabin Wang, Hui Zhang, Deren Yang
Summary: A novel casting method was developed to grow beta-Ga2O3 bulk single crystals without using a seed crystal. High-quality beta-Ga2O3 single crystal ingots with different orientations were obtained, exhibiting good crystal quality and low defect density. A numerical simulation model was proposed to explain the crystal growth process in the casting method.
JOURNAL OF ALLOYS AND COMPOUNDS
(2023)
Article
Chemistry, Physical
Ali Hajian, Thomas Konegger, Konrad Bielecki, Bjoern Mieller, Torsten Rabe, Sabine Schwarz, Christopher Zellner, Ulrich Schmid
Summary: The study systematically investigated the impact of solution concentration on the porosification of LTCC with H3PO4 as an etching solution, achieving substantial improvement. It also explored the effect of intermediate pH values and the use of PBS as a prospective novel etchant mixture.
JOURNAL OF ALLOYS AND COMPOUNDS
(2021)
Article
Materials Science, Coatings & Films
Lingyu Meng, A. F. M. Anhar Uddin Bhuiyan, Zixuan Feng, Hsien-Lien Huang, Jinwoo Hwang, Hongping Zhao
Summary: In this study, the MOCVD growth of (100) beta-Ga2O3 on on-axis Ga2O3 substrates was comprehensively investigated. The dependence of growth conditions on surface morphology, growth rate, and electron transport properties of the thin films was studied. The results provide a fundamental understanding of MOCVD epitaxy and the limitations of electron transport properties in (100) beta-Ga2O3 thin films grown along the on-axis (100) crystal orientation.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2022)
Article
Chemistry, Multidisciplinary
Shan Ding, Liying Zhang, Yuewen Li, Xiangqian Xiu, Zili Xie, Tao Tao, Bin Liu, Peng Chen, Rong Zhang, Youdou Zheng
Summary: In this study, large-scale and vertically aligned beta-Ga2O3 nanotube and microtube arrays were fabricated on a GaN template using a selective etching method based on different etching characteristics between GaN and Ga2O3. These micro/nanotubes have uniform morphology, controllable size, and adjustable wall thickness, demonstrating potential for novel optoelectronic devices.
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
Chemistry, Physical
Bo Fu, Guangzhong Jian, Gaohang He, Boyuan Feng, Wenxiang Mu, Yang Li, Zhitai Jia, Yanbin Li, Shibing Long, Sunan Ding, Yujun Shi, Xutang Tao
Summary: This study explores the structural, thermal, optical, and electrical properties of beta-Ga2O3 (101) plane with high-density surface dangling bonds for the first time, and finds that its potential applications are comparable to the widely used (201) plane through comprehensive comparisons with other common planes.
JOURNAL OF ALLOYS AND COMPOUNDS
(2021)
Article
Nanoscience & Nanotechnology
A. F. M. Anhar Uddin Bhuiyan, Lingyu Meng, Hsien-Lien Huang, Jith Sarker, Chris Chae, Baishakhi Mazumder, Jinwoo Hwang, Hongping Zhao
Summary: Phase pure beta-(AlxGa(1-x))(2)O-3 thin films were successfully grown on (001) oriented beta-Ga2O3 substrates using metalorganic chemical vapor deposition. The epitaxial growth of coherently strained beta-(AlxGa(1-x))(2)O-3 films with up to 25% Al compositions was achieved, as confirmed by high resolution x-ray diffraction. The presence of alloy inhomogeneity and local segregation of Al along the (201) plane was observed from atomic resolution STEM imaging, resulting in wavy and inhomogeneous interfaces in the beta-(AlxGa(1-x))(2)O-3/beta-Ga2O3 superlattice structure.
Article
Engineering, Electrical & Electronic
Yang Liu, Lai Wang, Yuantao Zhang, Xin Dong, Xiankai Sun, Zhibiao Hao, Yi Luo, Changzheng Sun, Yanjun Han, Bing Xiong, Jian Wang, Hongtao Li
Summary: In this study, a high-performance Ga2O3-based heterojunction diode was successfully fabricated using lift-off and transfer-print techniques. The diodes exhibited excellent electrical properties, indicating a new pathway for the fabrication of Ga2O3 heterojunctions and bipolar devices.
IEEE ELECTRON DEVICE LETTERS
(2021)
Article
Chemistry, Multidisciplinary
Khakimjon Saidov, Ivan Erofeev, Zainul Aabdin, Antoine Pacco, Harold Philipsen, Antony Winata Hartanto, Yifan Chen, Hongwei Yan, Weng Weei Tjiu, Frank Holsteyns, Utkur Mirsaidov
Summary: A method of precise and uniform wet etching for molybdenum (Mo) and other metals is presented, which overcomes the challenge of non-uniform etch profiles in wet chemical etching of polycrystalline metals. This method combines multiple cycles of cryo-oxidation and selective oxide dissolution to achieve the desired smooth and uniform nanostructures.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Chemistry, Physical
Yong Ha Choi, Kwang Hyeon Baik, Suhyun Kim, Jihyun Kim
Summary: The etching process of beta-Ga2O3 semiconductor using phosphoric acid as demonstrated in this study showed an anisotropic etch pit formation along the [001] direction. The new exposed facet (-201) was found to be stable, and the optoelectronic performance was greatly improved through the effective removal of defects by PEC etching.
APPLIED SURFACE SCIENCE
(2021)
Article
Physics, Applied
Hironori Okumura, Yuji Kato, Takayoshi Oshima, Tomas Palacios
JAPANESE JOURNAL OF APPLIED PHYSICS
(2019)
Article
Physics, Applied
Yuji Kato, Masataka Imura, Yoshiko Nakayama, Masaki Takeguchi, Takayoshi Oshima
APPLIED PHYSICS EXPRESS
(2019)
Article
Physics, Applied
Takayoshi Oshima, Yuji Kato, Eisuke Magome, Eiichi Kobayashi, Kazutoshi Takahashi
JAPANESE JOURNAL OF APPLIED PHYSICS
(2019)
Article
Engineering, Electrical & Electronic
Toshiyuki Oishi, Kosuke Urata, Makoto Hashikawa, Kosuke Ajiro, Takayoshi Oshima
IEEE ELECTRON DEVICE LETTERS
(2019)
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
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)
Article
Nanoscience & Nanotechnology
Yuma Kato, Muneaki Yamamoto, Akiyo Ozawa, Yu Kawaguchi, Akinobu Miyoshi, Takayoshi Oshima, Kazuhiko Maeda, Tomoko Yoshida
E-JOURNAL OF SURFACE SCIENCE AND NANOTECHNOLOGY
(2018)