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
Materials Science, Multidisciplinary
Galia Pozina, Chih-Wei Hsu, Natalia Abrikossova, Carl Hemmingsson
Summary: In this study, Zn-doped beta-Ga2O3 layers were grown on sapphire (0001) using halide vapor-phase epitaxy, with Zn doping concentrations in the range of 6 x 10(18) to 2.5 x 10(20) cm(-3). Modeling of growth chamber and optimization of process parameters were carried out. Zn doping did not affect optical emission properties, but growth under oxygen-rich conditions and crystalline particle formation on layer surface modified beta-Ga2O3 luminescence spectrum.
PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE
(2021)
Article
Engineering, Electrical & Electronic
Nikita Yakovlev, Aleksei Almaev, Pavel Butenko, David Tetelbaum, Alexey Mikhaylov, Alena Nikolskaya, Aleksei Pechnikov, Sergey Stepanov, Mikhail Boiko, Andrei Chikiryaka, Vladimir Nikolaev
Summary: The effect of Si+ ion implantation on the gas-sensing properties of (0001) alpha-Ga2O3 films grown by HVPE has been investigated. The results show that irradiation with a dose of 8 x 10(12) - 8 x 10(15) cm(-2) at an energy of 100 keV followed by postimplantation annealing significantly enhances the response of alpha-Ga2O3 films to 3 vol% of H-2 at 400 degrees C, reduces the response time by a factor of 6, and extends the operating temperature range to 30 degrees C. Additionally, alpha-Ga2O3 layers irradiated with a Si+ dose of 8 x 10(13) - 8 x 10(15) cm(-2) exhibit high sensitivity to CO and NH3 gases. A mechanism for the effect of Si+ ion irradiation on the gas-sensing properties of alpha-Ga2O3 structures is proposed.
IEEE SENSORS JOURNAL
(2023)
Article
Engineering, Electrical & Electronic
Yijun Zhang, Yiqing Gong, Xuanhu Chen, Yue Kuang, Jinggang Hao, Fang-Fang Ren, Shulin Gu, Rong Zhang, Jiandong Ye
Summary: In this study, single-domain heteroepitaxy of orthorhombic kappa-Ga2O3 epilayers on sapphire was achieved using the halide vapor-phase epitaxy (HVPE) technique, showing excellent microstructures and optical characteristics. Through proper phase engineering, defect-free single-domain structure was ultimately obtained, providing the possibility to investigate the intriguing ferroelectric behavior of kappa-Ga2O3 and design power devices with improved performance.
ACS APPLIED ELECTRONIC MATERIALS
(2022)
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
Crystallography
Galia Pozina, Chih-Wei Hsu, Natalia Abrikossova, Carl Hemmingsson
Summary: The growth process of high-quality Ga2O3 layers was optimized by modifying the gas inlet design, leading to improved growth uniformity. Replacing the conventional tube with a shower head effectively reduced the fluctuation of the Ga/O ratio.
Article
Physics, Applied
Yeong Je Jeong, Ji-Hyeon Park, Min Jae Yeom, Inho Kang, Jeong Yong Yang, Hyeong-Yun Kim, Dae-Woo Jeon, Geonwook Yoo
Summary: Heteroepitaxial alpha-Ga₂O₃ MOSFETs with a breakdown voltage of 2.3 kV were reported, and improved device performance was achieved through modified electrode structure and growth method.
APPLIED PHYSICS EXPRESS
(2022)
Article
Engineering, Electrical & Electronic
Hiroyuki Nishinaka, Tatsuji Nagaoka, Yuki Kajita, Masahiro Yoshimoto
Summary: Utilizing mist chemical vapor deposition (CVD) process, rapid homoepitaxial growth of beta-Ga2O3 thin films with smooth surfaces was achieved using a concentrated aqueous solution of GaCl3 precursor.
MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING
(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
Yuichi Oshima, Elaheh Ahmadi
Summary: Ultra-wide-bandgap (UWBG) semiconductors, including alpha-Ga2O3, have attracted attention for high-performance power devices. Alpha-Ga2O3 shows promise due to its large bandgap energy, band engineering flexibility, and ability to form hetero p-n junctions. Despite high dislocation density, preliminary prototype devices have been demonstrated. This Perspective provides an overview of alpha-Ga2O3 research for power devices and discusses future directions.
APPLIED PHYSICS LETTERS
(2022)
Article
Physics, Applied
Kazuki Ohnishi, Seiya Kawasaki, Naoki Fujimoto, Shugo Nitta, Hirotaka Watanabe, Yoshio Honda, Hiroshi Amano
Summary: A vertical GaN p(+)-n junction diode with an ideal breakdown voltage was successfully grown by halide vapor phase epitaxy (HVPE). The steep p(+)-n interface was observed and no Si-accumulating layer was formed due to continuous growth. This method offers improved electrical properties compared to regrowth of p-type GaN layers, with a minimum ideality factor of approximately 1.6.
APPLIED PHYSICS LETTERS
(2021)
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
Materials Science, Coatings & Films
Fedor Hrubisak, Kristina Husekova, Xiang Zheng, Alica Rosova, Edmund Dobrocka, Milan Tapajna, Matej Micusik, Peter Nadazdy, Fridrich Egyenes, Javad Keshtkar, Eva Kovacova, James W. Pomeroy, Martin Kuball, Filip Gucmann
Summary: In this study, monoclinic ss-Ga2O3 and orthorhombic kappa-Ga2O3 thin films were grown on highly thermally conductive 4H-SiC substrates using liquid-injection metal-organic chemical vapor deposition. Both gallium precursors produced the ss phase, but only the latter led to growth of kappa-Ga2O3. The best growth conditions for ss-Ga2O3 were a temperature of 700 degrees C and O-2 flows in the range of 600-800 SCCM. For kappa-Ga2O3, a narrow growth window was observed, with the best results at a temperature of 600 degrees C and an O-2 flow of 800 SCCM. The results suggest the potential of integrating Ga2O3 and SiC for improved thermal management and reliability of future high power Ga2O3-based devices.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2023)
Article
Materials Science, Multidisciplinary
Zeming Li, Teng Jiao, Wancheng Li, Gaoqiang Deng, Wei Chen, Zhengda Li, Zhaoti Diao, Xin Dong, Baolin Zhang, Yuantao Zhang, Zengjiang Wang, Guotong Du
Summary: Beta-Ga2O3 is a promising material for solar-blind UV detection, and the crystal quality significantly affects the performance of photodetectors. In this study, high quality homoepitaxial beta-Ga2O3 films were grown by MOCVD for SBUV PD fabrication, demonstrating excellent performance for both photoconductor PD and SBD PD. The responsivity and EQE of photoconductor PD were 1.08 A/W and 5.32 x 102% under 254nm illumination, while the I-254/Idark and rejection ratio of SBD PD were 320 and 42, respectively.
Article
Chemistry, Multidisciplinary
Hoki Son, Ye-ji Choi, Soon-Ku Hong, Ji-Hyeon Park, Dae-Woo Jeon
Summary: This study found that alpha-Ga2O3 grown on conical frustum-patterned sapphire substrates exhibited better crystal quality compared to those grown on conventional sapphire substrates, with improvements in surface morphology and reduction in threading dislocation propagation.
Article
Physics, Applied
Xiang Zheng, Taylor Moule, James W. Pomeroy, Masataka Higashiwaki, Martin Kuball
Summary: A new method for measuring temperature in semiconductor devices is proposed in this study, with a focus on minimizing the interference from trapping effects. Results show that there is a certain degree of error in the channel temperature measured using drain current, with the actual channel temperature being the average value between the source and drain contacts.
APPLIED PHYSICS LETTERS
(2022)
Article
Physics, Applied
Jianbo Liang, Daiki Takatsuki, Masataka Higashiwaki, Yasuo Shimizu, Yutaka Ohno, Yasuyoshi Nagai, Naoteru Shigekawa
Summary: In this work, Ga2O3(001)/Si(100) and Ga2O3(010)/Si(100) heterointerfaces were fabricated through surface activated bonding at room temperature. The thermal stability of the heterointerfaces was investigated by heating the bonding samples at different temperatures and it was found that the heterointerface with a thin Si exhibited good thermal stability at 1000 degrees C. An intermediate layer was formed at both heterointerfaces, with the Ga2O3(001)/Si(100) heterointerface having a uniform thickness while the Ga2O3(010)/Si(100) heterointerface having a non-uniform thickness.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2022)
Article
Physics, Applied
Zhenwei Wang, Daiki Takatsuki, Jianbo Liang, Takahiro Kitada, Naoteru Shigekawa, Masataka Higashiwaki
Summary: We studied the electrical properties of n-Si/n-Ga2O3 heterojunctions fabricated by surface-activated bonding. By analyzing temperature-dependent current density-voltage characteristics, we obtained the energy barrier heights at the Si/Ga2O3 interface for different reverse voltages. The conduction band offset at the heterointerface was estimated, and the non-uniform distribution of charged interface states was found to contribute to the spatially inhomogeneous energy barrier heights. The density of shallow interface states was also extracted from the reverse current density-voltage characteristics.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Nanoscience & Nanotechnology
Andrew J. Green, James Speck, Grace Xing, Peter Moens, Fredrik Allerstam, Krister Gumaelius, Thomas Neyer, Andrea Arias-Purdue, Vivek Mehrotra, Akito Kuramata, Kohei Sasaki, Shinya Watanabe, Kimiyoshi Koshi, John Blevins, Oliver Bierwagen, Sriram Krishnamoorthy, Kevin Leedy, Aaron R. Arehart, Adam T. Neal, Shin Mou, Steven A. Ringel, Avinash Kumar, Ankit Sharma, Krishnendu Ghosh, Uttam Singisetti, Wenshen Li, Kelson Chabak, Kyle Liddy, Ahmad Islam, Siddharth Rajan, Samuel Graham, Sukwon Choi, Zhe Cheng, Masataka Higashiwaki
Summary: Gallium Oxide has become a leading ultra-wide band gap semiconductor technology due to its favorable material properties. This roadmap presents the current state-of-the-art and future challenges in the field, aiming to enhance device performance and design efficient microelectronic systems.
Article
Physics, Applied
Sandeep Kumar, Hisashi Murakami, Yoshinao Kumagai, Masataka Higashiwaki
Summary: This study presents vertical Ga2O3 Schottky barrier diodes (SBDs) with a staircase field plate on a deep trench filled with SiO2, which effectively alleviates electric field concentration in the Ga2O3 drift layer and the SiO2 layer at high reverse voltage operation. The Ga2O3 SBDs demonstrate superior device characteristics with low on-resistance and high off-state breakdown voltage.
APPLIED PHYSICS EXPRESS
(2022)
Article
Physics, Applied
Rie Togashi, Haruka Ishida, Ken Goto, Masataka Higashiwaki, Yoshinao Kumagai
Summary: Thermodynamic analyses were conducted to study the growth of beta-Ga2O3 using ozone and plasma-assisted molecular beam epitaxy (MBE). The study found that the growth mechanism depended on the input VI/III ratio. Under O-rich conditions, the driving force for beta-Ga2O3 growth increased linearly with increasing Ga input partial pressure, while under Ga-rich conditions, the driving force decreased, leading to etching of beta-Ga2O3. Furthermore, the use of ozone allowed growth at higher temperatures compared to O radicals.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
Kyohei Nitta, Kohei Sasaki, Akito Kuramata, Hisashi Murakami
Summary: This study uses Trihalide Vapor Phase Epitaxy (THVPE) with solid GaCl3 as a group III precursor to successfully grow beta-Ga2O3, showing a linear increase in growth rate with increasing precursor pressure. The relationship between growth rate and VI/III ratio is investigated on sapphire substrates, with the maximum growth rate achieved at a VI/III ratio of 95. A growth rate of 32.2 μm/h is achieved on beta-Ga2O3 (001) substrates, with no particle generation, equivalent crystal quality to the substrate, and high purity comparable to HVPE.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
Rie Togashi, Ken Goto, Masataka Higashiwaki, Yoshinao Kumagai
Summary: Thermodynamic analyses were performed to study the growth of group-III sesquioxides by ozone and plasma-assisted MBE. The driving force for III2O3 growth increased with increasing input partial pressure of the group-III metal under O-rich conditions, but decreased under group-III-metal-rich conditions. This decrease was caused by the formation of Ga2O or In2O during growth. Ga and In droplets formed at low temperatures, while Al droplets were formed at high temperatures, with the growth order being c-In2O3 < ss-Ga2O3 << alpha-Al2O3.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
Zhenwei Wang, Takahiro Kitada, Daiki Takatsuki, Jianbo Liang, Naoteru Shigekawa, Masataka Higashiwaki
Summary: In this study, p-Si/n-Ga2O3 and p(+)-Si/n-Ga2O3 heterostructures were fabricated using surface-activated bonding technique, and their electrical properties were investigated. Current density-voltage measurement before and after thermal annealing at 450 ? showed a significant increase in current density after annealing, which was attributed to thinning of the intermediate layer formed during the bonding process. Distinctive two-stage capacitance-voltage characteristics were observed for p-Si/n-Ga2O3 heterostructures, and numerical calculation considering the effect of two-dimensional electron gas formed at the heterointerface reproduced these characteristics well. These results indicate that Ga2O3-based p-n heterostructures with good interface properties and large-area uniformity can be fabricated using surface-activated bonding.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Materials Science, Coatings & Films
Ken Goto, Taro Nishimura, Masato Ishikawa, Takahito Okuyama, Haruka Tozato, Shogo Sasaki, Kazutada Ikenaga, Yoshihiko Takinami, Hideaki Machida, Yoshinao Kumagai
Summary: The suitability of diethylgallium ethoxide (Et2GaOEt) as a precursor for beta-gallium oxide (beta-Ga2O3) growth was investigated. The growth behavior of Et2GaOEt was estimated through pyrolysis and combustion processes. The results showed that Et2GaOEt could be decomposed and combusted to gallane, ethylene, and acetaldehyde. It was found that Et2GaOEt was suitable for MOVPE growth of beta-Ga2O3, with performance comparable to triethylgallium (Et3Ga).
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2023)
Article
Physics, Condensed Matter
Iori Kobayashi, Ryohei Hieda, Hiroto Murata, Hisashi Murakami
Summary: In this study, the impact of intermediate layers on ScAlMgO4 (SAM) for high-speed InGaN growth using trihalide vapor-phase epitaxy (THVPE) was investigated. The coverage and thickness of the intermediate layer significantly affected the composition and crystalline quality. THVPE was successfully used to fabricate InGaN with 17% indium on SAM in a lattice-matched state, demonstrating the potential for high-quality InGaN quasi-substrates with high indium composition.
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS
(2023)
Article
Materials Science, Coatings & Films
Takumi Ohtsuki, Masataka Higashiwaki
Summary: We systematically studied the relationship between the structural properties of (AlxGa1-x)(2)O-3 thin films grown on ss-Ga2O3 (010) substrates and the composition of Al. Crystal structure characterization was performed using X-ray diffraction, and surface morphology was observed using reflection high-energy electron diffraction and atomic force microscopy. Defects appeared on the surface and crystallinity began to degrade when the Al composition x exceeded approximately 0.16 in the 100-nm-thick thin films. The defects mainly developed along the [201] direction and slightly along the [001] direction as x increased. The boundary where the thin film quality changed was close to a critical thickness curve calculated using the Matthews-Blakeslee model assuming the slip system of <201>{10(2) over bar}.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2023)
Article
Nanoscience & Nanotechnology
Ken Goto, Tomo Ueno, Yoshinao Kumagai
Summary: This study investigated the feasibility of using cation-exchange reactions (CERs) with metal chloride gases to form heterostructures of group-III sesquioxides. Thermodynamic analyses revealed that CERs with aluminum chloride gases can form aluminum oxide (Al2O3) layers on gallium oxide (Ga2O3) or indium oxide (In2O3) substrates, and CERs with gallium chloride gases can form Ga2O3 layers on In2O3 substrates. However, CERs with gallium chloride gases or indium chloride gases did not occur on Al2O3 substrates, indicating the inability to form heterostructures.
Proceedings Paper
Engineering, Electrical & Electronic
C. De Santi, M. Fregolent, M. Buffolo, M. Higashiwaki, G. Meneghessoa, E. Zanonia, M. Meneghinia
Summary: This paper analyzes the electrical behavior and deep levels in nitrogen-implanted gallium oxide Schottky barrier diodes. The study investigates the feasibility of nitrogen implantation as an isolation procedure and the annealing process to eliminate defects. The results show a reduction in leakage current and the presence of electron trapping processes. The concentration of defects decreases with high-temperature annealing.
OXIDE-BASED MATERIALS AND DEVICES XIII
(2022)
