Article
Chemistry, Multidisciplinary
Jiaqi Wei, Fang Liu, Xin Rong, Tao Wang, Liuyun Yang, Renchun Tao, Jing Yang, Liwei Guo, Bo Shen, Xinqiang Wang
Summary: Unintentional nitrogen incorporation in beta-Ga2O3 films grown by plasma-assisted molecular beam epitaxy hinders n-type doping, while a quartz crucible free of nitrogen atoms can overcome this issue, allowing tunable electron concentration in the n-type beta-Ga2O3 films.
Article
Engineering, Electrical & Electronic
Xue-Qiang Ji, Chao Lu, Jin-Jin Wang, Meng-Cheng Li, Xiao-Hui Qi, Jian-Ying Yue, Lei Shu, Pei-Gang Li
Summary: This study presents an enhanced mode back-gated MOSFET based on a β-Ga2O3 film for solar-blind UV detection applications. By depleting the channel through gate modulation, the MOS device achieves a significant reduction in dark current and greatly improves the photoconductivity performance through the dual regulation of light intensity and gate voltage.
IEEE SENSORS JOURNAL
(2023)
Article
Materials Science, Coatings & Films
Michael A. Mastro, Charles R. Eddy, Marko J. Tadjer, Jennifer K. Hite, Jihyun Kim, Stephen J. Pearton
Summary: Recent advancements in bulk crystal growth of beta-Ga2O3 have led to commercialization of large-area substrates and high-quality films on (010) substrates, revealing subnanometer-scale facets and larger ridges on the surface. Recommendations for standardizing substrates to control ridge formation have been proposed based on density function theory calculations.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2021)
Article
Engineering, Electrical & Electronic
Guangming Qu, Siyuan Xu, Lining Liu, Minglei Tang, Songhao Wu, Chunyang Jia, Xingfei Zhang, Wurui Song, Young Jin Lee, Jianlong Xu, Guodong Wang, Yuanxiao Ma, Ji-Hyeon Park, Yiyun Zhang, Xiaoyan Yi, Yeliang Wang, Jinmin Li
Summary: In this work, a normally-on single-monocrystal beta-Ga2O3 nanowire back-gate field-effect transistor (FET) was successfully demonstrated. The FET showed a high on/off ratio and low leakage current density. However, the on/off ratio rapidly degraded at high temperatures due to the activation of self-trapped holes and intrinsic vacancy-related defects, leading to an increase in channel leakage current.
SEMICONDUCTOR SCIENCE AND TECHNOLOGY
(2022)
Article
Physics, Applied
Youngbin Yoon, Min Ju Kim, Byung Jin Cho, Myunghun Shin, Wan Sik Hwang
Summary: Monoclinic gallium oxide (β-Ga2O3) is of interest in the scientific community for its application in power electronics, particularly in devices requiring handling of high voltage. Research has shown that 8-nm-thick Sn-doped polycrystalline β-Ga2O3 thin films have a large optical bandgap and high voltage handling capacity, making them suitable for various fields beyond power electronics.
APPLIED PHYSICS LETTERS
(2021)
Article
Physics, Applied
Siyuan Xu, Lining Liu, Guangming Qu, Xingfei Zhang, Chunyang Jia, Songhao Wu, Yuanxiao Ma, Young Jin Lee, Guodong Wang, Ji-Hyeon Park, Yiyun Zhang, Xiaoyan Yi, Yeliang Wang, Jinmin Li
Summary: In this study, a fin field-effect transistor (FinFET) based on a β-Ga2O3 nanowire with a diameter of approximately 60nm on a Si substrate was demonstrated. The device showed excellent performance with high on/off ratio, low leakage current, and low subthreshold swing. Simulation results were consistent with experimental measurements, and trap-related 1/f noise and 1/f^2 noise were identified through low frequency noise analysis.
APPLIED PHYSICS LETTERS
(2022)
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
Materials Science, Coatings & Films
Michael A. Mastro, Marko J. Tadjer, Jihyun Kim, Fan Ren, Stephen J. Pearton
Summary: The design of beta-Ga2O3-based modulation-doped field effect transistors focuses on the role of self-heating and the resulting modification of the electron mobility profile. It is found that a decrease in drain current is attributed to position-dependent mobility reduction. Additionally, an undesired secondary channel can form at the modulation-doped layer.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2021)
Article
Materials Science, Coatings & Films
William A. Callahan, Edwin Supple, David Ginley, Michael Sanders, Brian P. Gorman, Ryan O'Hayre, Andriy Zakutayev
Summary: Beta gallium oxide (beta-Ga2O3) shows great potential for high-temperature, high-power, and sensing electronics applications. However, stable metallization layers for Ohmic contacts at high temperatures have been a challenge. In this study, we demonstrate stable Ohmic contacts for Ga2O3 devices operating at temperatures up to 500-600 degrees C using ultrathin Ti layers with a self-limiting interfacial reaction.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2023)
Article
Chemistry, Multidisciplinary
Chloe Leblanc, Dinusha Herath Mudiyanselage, Seunguk Song, Huairuo Zhang, Albert V. Davydov, Houqiang Fu, Deep Jariwala
Summary: In this study, we successfully fabricated and optimized 2D/3D vertical diodes on beta-Ga2O3 by varying substrate planar orientation, choice of 2D material, and metal contacts. The quality of the devices was validated through high-temperature dependent measurements, atomic-force microscopy techniques, and technology computer-aided design simulations. The findings suggest that 2D/3D beta-Ga2O3 vertical heterojunctions optimized by specific factors show promising potential for application in power rectifiers.
Article
Engineering, Electrical & Electronic
Daniel M. Dryden, Kyle J. Liddy, Ahmad E. Islam, Jeremiah C. Williams, Dennis E. Walker, Nolan S. Hendricks, Neil A. Moser, Andrea Arias-Purdue, Nicholas P. Sepelak, Kursti DeLello, Kelson D. Chabak, Andrew J. Green
Summary: We demonstrate a passivated MESFET fabricated on (010) Si-doped beta-Ga2O3 with breakdown over 2.4 kV without field plates, high Power Figure of Merit (PFOM), and high estimated Huang's Material Figure of Merit (HMFOM), owing to low gate charge and high breakdown. MESFETs with 13 μm source-drain spacing and 75 nm channel exhibited a current density of 61 mA/mm, peak transconductance of 27 mS/mm, and on-resistance of 133 Ω•mm. The device showed a PFOM competitive with state-of-the-art beta-Ga2O3 devices and a record high estimated HMFOM for a beta-Ga2O3 device, competitive with commercial wide-band gap devices. This demonstrates high-performance beta-Ga2O3 devices as viable multi-kV high-voltage power switches.
IEEE ELECTRON DEVICE LETTERS
(2022)
Article
Physics, Applied
Nidhin Kurian Kalarickal, Ashok Dheenan, Joe. F. F. McGlone, Sushovan Dhara, Mark Brenner, Steven. A. A. Ringel, Siddharth Rajan
Summary: We presented the design and fabrication of beta-Ga2O3 self-aligned lateral MOSFETs with a heavily doped beta-Ga2O3 cap layer. The fabricated device achieved a record high DC drain current density of 560 mA/mm at 5V drain bias, although the current density was limited by excessive self-heating. However, pulsed I-V measurements showed a record high current density of 895 mA/mm and a high transconductance of 43 mS/mm, indicating reduced self-heating in the device. These findings are promising for the development of high power density devices based on beta-Ga2O3.
APPLIED PHYSICS LETTERS
(2023)
Article
Crystallography
Lei Ge, Qiu Chen, Shuai Wang, Wenxiang Mu, Qian Xin, Zhitai Jia, Mingsheng Xu, Xutang Tao, Aimin Song
Summary: In this study, beta-Ga2O3 field-effect transistors (FETs) were fabricated with local thinning to change the threshold voltage. Device simulation confirmed that the local thinning structure is an effective method to enable enhancement-mode Ga2O3 FETs.
Article
Engineering, Electrical & Electronic
Qiwen Kong, Long Liu, Zijie Zheng, Chen Sun, Zuopu Zhou, Leming Jiao, Annie Kumar, Rui Shao, Jishen Zhang, Haiwen Xu, Yue Chen, Bich-Yen Nguyen, Xiao Gong
Summary: We present a 3-D oxide semiconductor fin-gate ferroelectric field-effect transistor (Fe-FET) compatible with back-end-of-line (BEOL) process. Our Fe-FETs utilize atomic layer deposition (ALD)-grown zinc oxide (ZnO) channel and Zr-doped HfO2 (HZO) ferroelectric dielectric, which conformally cover the fin-shaped tungsten (W) metal gate with uniform thickness on all surfaces. These devices demonstrate excellent electrical characteristics, including large memory windows, high endurance, long-term retention, robust ON/OFF ratio, and good linearity, making them highly promising for future ultrahigh-density 3-D integrated computing applications.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Article
Nanoscience & Nanotechnology
Hagyoul Bae, Tae Joon Park, Jinhyun Noh, Wonil Chung, Mengwei Si, Shriram Ramanathan, Peide D. Ye
Summary: Nano-membrane tri-gate beta-Gallium oxide field-effect transistors fabricated via exfoliation on SiO2/Si substrate demonstrate excellent performance, with extremely low subthreshold slope, high drain current ON/OFF ratio, stable transfer characteristics, and robustness at high temperatures up to 400 degrees C.
Article
Physics, Applied
Jian-Sian Li, Chao-Ching Chiang, Xinyi Xia, Sergei Stepanoff, Aman Haque, Douglas E. Wolfe, Fan Ren, S. J. Pearton
Summary: NiO/Ga2O3 heterojunction rectifiers were irradiated with 1 Mrad of Co-60 gamma-rays, resulting in a 1000x reduction in forward current, a 100x increase in reverse current, and a significant decrease in the on-off ratio. The carrier concentration in the Ga2O3 drift region slightly decreased, indicating a reversible effect. The rectifiers showed no permanent ionizing dose effects and resistance to displacement damage, suggesting potential applications in harsh radiation environments with appropriate bias sequences.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Materials Science, Coatings & Films
Jian-Sian Li, Xinyi Xia, Chao-Ching Chiang, David C. C. Hays, Brent P. P. Gila, Valentin Craciun, Fan Ren, S. J. Pearton
Summary: The characteristics of sputtered NiO for pn heterojunctions with Ga2O3 were investigated, and it was found that the oxygen/nickel and Ni2O3/NiO ratios, as well as the bandgap and resistivity, increased with the O-2/Ar gas flow ratio. However, the bandgap and Ni2O3/NiO ratio decreased with increasing annealing temperature, resulting in higher film density. The incorporation of hydrogen into NiO during plasma exposure was confirmed, and the band alignments of NiO films with both alpha- and beta-Ga2O3 were determined to have type II-staggered gaps. The breakdown voltage of NiO/beta-Ga2O3 heterojunction rectifiers also varied with the O-2/Ar flow ratio during deposition.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2023)
Article
Materials Science, Coatings & Films
Benjamin C. Letson, Simon Barke, Peter Wass, Guido Mueller, Fan Ren, Stephen J. Pearton, John W. Conklin
Summary: The laser interferometer space antenna (LISA), a joint ESA and NASA project, will enable space-based gravitational wave detection. Three identical spacecraft will form a triangular configuration, flying in a drag-free formation around free-falling test masses. To compensate for test mass charging, UV photons with higher energy than gold's work function are needed. The performance of UV light emitting diodes (LEDs) for the LISA mission was characterized under various operating conditions, and degradation was found to be faster at elevated temperatures and in dc conditions. Preselection based on initial spectral ratio and ideality factor showed positive correlation with subsequent reliability. The UV LEDs for LISA are required to support a 2-year cruise and commissioning period, followed by a 4-year science mission.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2023)
Article
Engineering, Electrical & Electronic
Chao-Ching Chiang, Chan-Wen Chiu, Fan Ren, Cheng-Tse Tsai, Yu-Te Liao, Josephine F. Esquivel-Upshaw, Stephen J. Pearton
Summary: This study presents a SARS-CoV-2 virus detection mechanism using stored disposable strips. The accuracy of this sensing platform is comparable to PCR and provides results in less than 30 seconds. The disposable strips, biofunctionalized with SARS-CoV-2 antibodies, detect the virus in saliva samples, and the detected signals are amplified and displayed on an LCD screen. The system demonstrates the ability to show qualitative results within 30 seconds and quantitative concentrations in 5 minutes.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B
(2023)
Article
Engineering, Electrical & Electronic
Minghan Xian, Jenna L. Stephany, Chan-Wen Chiu, Chao-Ching Chiang, Fan Ren, Cheng-Tse Tsai, Siang-Sin Shan, Yu-Te Liao, Josephine F. Esquivel-Upshaw, Stephen J. Pearton
Summary: Oral squamous cell carcinoma is a common type of lip and oral cavity cancer, which requires early detection for improved survival rates. A modular biological sensor utilizing transistor-based technology has been developed for rapid and accurate point of care detection of the cancer, providing opportunities for quick clinical diagnosis.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B
(2023)
Article
Physics, Applied
Md Abu Jafar Rasel, Nahid Sultan Al-Mamun, Sergei Stepanoff, Aman Haque, Douglas E. Wolfe, Fan Ren, Stephen J. Pearton
Summary: In this work, we illustrate the rejuvenation of degraded Ti/4H-SiC Schottky barrier diodes at room temperature within seconds by utilizing high-energy electron interactions with defects. By applying high current density electrical pulsing with low frequency and duty cycle to suppress temperature rise, we successfully decrease defect concentration and improve device performance beyond the pristine condition. The ultrafast and room temperature process has the potential to rejuvenate electronic devices in high power and harsh environmental conditions.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
Md Abu Jafar Rasel, Ryan Schoell, Nahid Sultan Al-Mamun, Khalid Hattar, C. Thomas Harris, Aman Haque, Douglas E. Wolfe, Fan Ren, Stephen J. Pearton
Summary: This study investigated the effects and mechanism of IL-37 on pyroptosis in RA-FLSs induced by TNF-a. It was found that IL-37 inhibited inflammation and reduced pyroptosis-related protein expression in RA-FLSs. The study also revealed that IL-37 alleviates TNF-a-induced pyroptosis in RA-FLSs by inhibiting NF-?B/GSDMD signaling.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2023)
Article
Materials Science, Coatings & Films
A. Y. Polyakov, A. I. Kochkova, Amanda Langorgen, Lasse Vines, A. Vasilev, I. V. Shchemerov, A. A. Romanov, S. J. Pearton
Summary: The study investigates the relationship between the emission rate of deep traps called E1 traps and the electric field dependence. The results demonstrate that the activation energy of the centers and the ratio of high-field to low-field electron emission rates follow a linear relationship with the square root of electric field at a fixed temperature, indicating the deep donor behavior of these traps. The possible microscopic nature of these centers is discussed based on recent theoretical calculations, and the most likely candidates are proposed to be Si-Ga1-H or Sn-Ga2-H complexes.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2023)
Review
Materials Science, Multidisciplinary
Benjamin C. Letson, John W. Conklin, Peter Wass, Simon Barke, Guido Mueller, Md Abu Jafar Rasel, Aman Haque, Stephen J. Pearton, Fan Ren
Summary: There are various applications for deep UV AlGaN Light-Emitting Diodes (LEDs), including virus inactivation, air and water purification, sterilization, bioagent detection, and UV polymer curing. The long-term stability of these LEDs is important for space missions such as the Laser Interferometer Space Antenna (LISA). The literature review shows that the decline in output power of these LEDs over extended operating times is mainly driven by current and temperature, with the degradation rate dependent on the cube of drive current density and exponentially on temperature. The main mechanism for this decline is believed to be the creation/migration of point defects. Pre-screening based on the ratio of band edge-to-midgap emission and LED ideality factor can identify devices with long lifetimes (>10,000 h).
ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY
(2023)
Article
Engineering, Electrical & Electronic
Sergei P. Stepanoff, Aman Haque, Fan Ren, Stephen Pearton, Douglas E. Wolfe
Summary: The susceptibility of electronics to radiation increases as the size and complexity of electronic chips or systems increase. This study develops an indirect technique to identify radiation-susceptible regions and demonstrates its effectiveness in rapid detection.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B
(2023)
Article
Chemistry, Physical
Chao-Ching Chiang, Xinyi Xia, Jian-Sian Li, Fan Ren, S. J. Pearton
Summary: The 8-polytype of Ga2O3 is a promising material for next generation power electronics and solar-blind UV photodetectors due to its high critical electric field strength and ability to be grown as large diameter single crystals. Dry etching is being focused on for patterning such devices, but it may cause surface modification and damage to the material. This study demonstrates that dry etch damage in 8-Ga2O3 leads to a reduction in near-surface carrier concentration, affecting device parameters like on-state resistance and introducing trap-assisted space-charge-limited conduction in the damaged layers.
APPLIED SURFACE SCIENCE
(2023)
Article
Materials Science, Multidisciplinary
Jian-Sian Li, Xinyi Xia, Chao-Ching Chiang, Hsiao-Hsuan Wan, Fan Ren, Jihyun Kim, S. J. Pearton
Summary: Neutrons generated by charge-exchange reactions were used to irradiate Schottky Ga2O3 rectifiers and NiO/Ga2O3 p-n heterojunction rectifiers. The breakdown voltage was improved for Schottky rectifiers but highly degraded for their NiO/Ga2O3 counterparts. The switching characteristics were degraded for both types of devices after irradiation.
ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY
(2023)
Article
Materials Science, Multidisciplinary
Jian-Sian Li, Chao-Ching Chiang, Xinyi Xia, Hsiao-Hsuan Wan, Fan Ren, S. J. Pearton
Summary: Large area vertical NiO/β n-Ga2O/n(+) Ga2O3 heterojunction rectifiers with high breakdown voltage (3.6 kV) and large conducting currents (4.8 A) are demonstrated. The performance exceeds the unipolar 1D limit for GaN, indicating the potential of β-Ga2O3 for future high-power rectification devices. The breakdown voltage is strongly dependent on the carrier concentration in the drift region.
ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY
(2023)
Article
Crystallography
Chao-Ching Chiang, Jian-Sian Li, Hsiao-Hsuan Wan, Fan Ren, Stephen J. Pearton
Summary: Ga2O3 heterojunction rectifiers with NiO as the solution on the p-type side have become a novel candidate for power conversion applications. In this study, the optimized design of high-breakdown NiO/Ga2O3 rectifiers was examined using the Silvaco TCAD simulator to determine the electric field distribution. The doping concentration, guard ring thickness, and extension beyond the anode were all important factors in determining the breakdown location. The transition phenomenon from the edge of the NiO extension to the top contact periphery was found to be correlated with the depletion effect.
Article
Engineering, Electrical & Electronic
Chao-Ching Chiang, Hsiao-Hsuan Wan, Jian-Sian Li, Fan Ren, Timothy Jinsoo Yoo, Honggyu Kim, S. J. Pearton
Summary: Sputtered p-NiO films were used to suppress gate leakage and produce a positive shift in the gate voltage of AlGaN/GaN high-electron mobility transistors for e-mode operation. The utility of NiO gates in increasing the on-off ratio and shifting the threshold voltage in comparison to Schottky gates was demonstrated.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B
(2023)
