Article
Physics, Applied
Lian Zhang, Zhe Cheng, Yawei He, Jianxing Xu, Lifang Jia, Xinyuan Wang, Shiyong Zhang, Wei Tan, Yun Zhang
Summary: This study focuses on the electron concentration and mobility of SAG n(+)-GaN on InAlN/GaN HEMTs using MOCVD, revealing that the electron mobility of SAG GaN is significantly affected by thickness. A gas flow model is proposed to guide the regrowth for improving electron mobility. High mobility and low resistance are achieved in the SAG GaN, contributing to the performance of the HEMTs.
APPLIED PHYSICS LETTERS
(2021)
Article
Materials Science, Multidisciplinary
Md Abu Jafar Rasel, Sergei Stepanoff, Aman Haque, Douglas E. Wolfe, Fan Ren, Stephen Pearton
Summary: This study investigates the influence of localized mechanical stress fields on defect nucleation sites under radiation in gallium nitride high-electron-mobility transistors (GaN HEMTs). The results show that tensile stressed localizations experience higher radiation-induced strain, which can be explained by the tensile stress dependence of the carrier concentration and mobility in the AlGaN layer.
PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS
(2022)
Article
Chemistry, Multidisciplinary
Chun-Yu Li, Chi-Ching Liu, Wei-Chih Lai, Yung-Chiang Lan, Yun-Chorng Chang
Summary: The study demonstrates the ability to exclude thermal effects and detect non-thermal hot carriers generated by surface plasmons using an AlGaN/GaN transistor. This ultra-sensitive platform shows at least two orders of magnitude more sensitivity compared to previous reports, offering a new way to optimize plasmonic nanoantenna design in various applications.
Article
Engineering, Electrical & Electronic
Injun Hwang, Soogine Chong, Younghwan Park, Sun-Kyu Hwang, Boram Kim, Joonyong Kim, Jaejoon Oh, Jun Hyuk Park, Dong-Chul Shin, Min Chul Yu, Jai Kwang Shin, Jongseob Kim
Summary: This study focuses on the transient measurement of the drift region potential in AlGaN/GaN HEMT under high power state, revealing that the propagation speed of high electric field in the device is influenced by the drift region voltage, and proposing that trapping of hot channel electrons is causing this effect.
IEEE ELECTRON DEVICE LETTERS
(2021)
Article
Physics, Applied
Yuwei Zhou, Minhan Mi, Mei Yang, Yutong Han, Pengfei Wang, Yilin Chen, Jielong Liu, Can Gong, Yiwei Lu, Meng Zhang, Qing Zhu, Xiaohua Ma, Yue Hao
Summary: By regrowing Ohmic contact with a contact ledge structure, high-performance millimeter-wave InAlN/GaN HEMT is fabricated for low voltage RF applications, showing improved output current density and power-added efficiency.
APPLIED PHYSICS LETTERS
(2022)
Article
Engineering, Electrical & Electronic
Nipun Sharma, Sumit Kumar, Ankur Gupta, Surani Bin Dolmanan, Dharmraj Subhash Kotekar Patil, Swee Tiam Tan, Sudhiranjan Tripathy, Mahesh Kumar
Summary: By employing MoS2 functionalization on AlGaN/GaN HEMTs sensors, the researchers have successfully developed a sensitive and selective gas sensor for NO2 detection at room temperature. The sensor exhibited enhanced sensing response and complete recovery without any external stimuli, making it a promising candidate for nitride-based integrated electronics.
SENSORS AND ACTUATORS A-PHYSICAL
(2022)
Article
Engineering, Electrical & Electronic
Shijie Pan, Shiwei Feng, Xuan Li, Xiang Zheng, Xiaozhuang Lu, Chaoxu Hu, Guojian Shao, Gang Lin
Summary: The effects of high-energy electron irradiation on the electrical and trapping properties of AlGaN/GaN HEMTs were systematically investigated. The study found that irradiation induced strain relaxation in the HEMT, resulting in improved electrical characteristics and reduced trap density. Additionally, traps in the device were identified and their behaviors were observed to change after irradiation.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2021)
Article
Materials Science, Coatings & Films
Stefan Schmult, Pascal Appelt, Claudia Silva, Steffen Wirth, Andre Wachowiak, Andreas Grosser, Thomas Mikolajick
Summary: Inconsistencies in the concentrations of unintentional donor impurities and free charge carriers in GaN/AlGaN layer stacks containing a two-dimensional electron gas (2DEG) can be explained by the measurement procedure and the method of extracting the free charge carrier concentration. When the 2DEG acts as the bottom electrode in capacitance versus voltage measurements, unphysically low concentrations of free charges are calculated due to the depletion of the 2DEG and the disappearance of the bottom electrode. It is shown that, for the case of a defined (non-vanishing) bottom electrode, the levels of donor impurities and resulting free charges consistently match.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2023)
Article
Physics, Applied
Mohammad Wahidur Rahman, Nidhin Kurian Kalarickal, Hyunsoo Lee, Towhidur Razzak, Siddharth Rajan
Summary: In this study, AlGaN/GaN HEMTs integrated with high permittivity BaTiO3 dielectric were discussed to enhance the breakdown characteristics. The use of high permittivity BaTiO3 dielectric layers prevented premature gate breakdown and enabled higher breakdown fields, leading to devices with high power figure of merit. This work demonstrates that electrostatic engineering with high-permittivity dielectrics can push AlGaN/GaN HEMTs closer to material breakdown field limits.
APPLIED PHYSICS LETTERS
(2021)
Article
Physics, Applied
Mei Ge, Yi Li, Youhua Zhu, Dunjun Chen, Zhiliang Wang, Shuxin Tan
Summary: The improved e-mode AlGaN/GaN HEMT with a gate stack beta-Ga2O3/p-GaN structure outperforms the conventional p-GaN gate HEMT, mainly due to the use of the beta-Ga2O3 layer which reduces the electric field strength in the gate region and decreases off-state leakage current. Additionally, there is a trade-off between the thickness of the beta-Ga2O3 layer and the performance of the device.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Engineering, Electrical & Electronic
Pengfei Wan, Jianqun Yang, Tao Ying, Gang Lv, Ling Lv, Shangli Dong, Lei Dong, Xueqiang Yu, Zhaofeng Zhen, Weiqi Li, Xingji Li
Summary: The study examined the electrical degradation in AlGaN/GaN HEMTs under irradiation with carbon, oxygen, and fluorine ions. Results showed that the output current and threshold voltage of HEMTs significantly decreased after a certain ion fluence, indicating radiation-induced performance degradation.
IEEE TRANSACTIONS ON NUCLEAR SCIENCE
(2021)
Article
Materials Science, Multidisciplinary
Jinjin Tang, Guipeng Liu, Bangyao Mao, Guijuan Zhao, Jianhong Yang
Summary: This paper systematically elucidates the physical mechanism of the GaN interlayer for improving the 2D electron gas (2DEG) mobility in the InGaN channel using an intersub-band scattering model. The results show that introducing a GaN interlayer can significantly improve the 2DEG mobility, and this effect is closely related to scattering mechanisms such as polar optical phonon scattering and alloy disorder scattering.
PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS
(2022)
Article
Physics, Multidisciplinary
Hao Zou, Lin-An Yang, Xiao-Hua Ma, Yue Hao
Summary: This study analyzes the effects of various notch structures on the performance of AlGaN/GaN HEMTs, showing that the double-notch structure HEMT has significant improvements in gate voltage swing, breakdown voltage, and cut-off frequency compared to conventional HEMTs, while also effectively suppressing current collapse.
Article
Physics, Multidisciplinary
Si-De Song, Su-Zhen Wu, Guo-Zhu Liu, Wei Zhao, Yin-Quan Wang, Jian-Wei Wu, Qi He
Summary: In this study, the degradation mechanisms of enhancement-mode p-GaN gate AlGaN/GaN high-electron mobility transistor were extensively analyzed under different stress conditions. The results showed that the device exhibited different electrical characteristics under various stress conditions, indicating excellent performance under reverse gate bias stress. These findings are significant in guiding process optimization towards a high voltage and highly reliable enhanced AlGaN/GaN high-electron mobility transistor.
Article
Materials Science, Multidisciplinary
Shaoqian Lu, Guohao Yu, Yingfei Sun, Xu Yuan, Zhongkai Du, Bingliang Zhang, Lu Wang, Yu Li, Dongdong Wu, Zengli Huang, Zhongming Zeng, Xulei Qin, Baoshun Zhang
Summary: In this article, a method of nitrogen plasma treatment is proposed to achieve normally off p-GaN/AlGaN/GaN high-electron-mobility transistors, and the related mechanism is proposed. The nitrogen plasma treatment depletes holes in the p-GaN layer and changes the surface characteristics, resulting in the formation of a 2D electron gas at the AlGaN/GaN interface. The device shows enhanced performance with improved threshold voltage, on/off ratio, and maximum drain current.
PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS
(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)
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
Crystallography
Jian-Sian Li, Hsiao-Hsuan Wan, Chao-Ching Chiang, Xinyi Xia, Timothy Jinsoo Yoo, Honggyu Kim, Fan Ren, Stephen J. Pearton
Summary: Vertical heterojunction rectifiers with p-type NiO and thick Ga2O3 drift layers grown on Sn-doped β-Ga2O3 substrates exhibited breakdown voltages > 8 kV. Low drift doping concentration, low power during NiO deposition, and the formation of a guard ring were key factors for achieving excellent performance. These results demonstrate the potential of NiO/Ga2O3 rectifiers beyond SiC and GaN.
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
Jian-Sian Li, Hsiao-Hsuan Wan, Chao-Ching Chiang, Fan Ren, Stephen J. Pearton
Summary: The stability of vertical geometry NiO/Ga2O3 rectifiers was examined under two types of annealing. It was found that annealing at 300 degrees C resulted in the best performance, including maximizing breakdown voltage and on-off ratio, lowering forward turn-on voltage, reducing reverse leakage current, and maintaining on resistance. The surface morphology remained smooth and the NiO exhibited a bandgap of 3.84 eV with an almost unity Ni2O3/NiO composition.
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
Materials Science, Multidisciplinary
Jian-Sian Li, Chao-Ching Chiang, Xinyi Xia, Hsiao-Hsuan Wan, Fan Ren, S. J. Pearton
Summary: NiO/β-Ga2O3 vertical rectifiers show near-temperature-independent breakdown voltages (V-B) of >8 kV at 600 K. The power figure of merit (V-B)²/R-ON for 100 μm diameter devices is 9.1 GW cm(-2) at 300 K and 3.9 GW cm(-2) at 600 K. In contrast, Schottky rectifiers on the same wafers have V-B of about 1100 V at 300 K with a negative temperature coefficient of breakdown. The power figure of merit for Schottky rectifiers is much lower compared to the heterojunction rectifiers. The results demonstrate the potential of using transparent oxide heterojunctions for high temperature, high voltage applications.
JOURNAL OF MATERIALS CHEMISTRY C
(2023)
Review
Engineering, Electrical & Electronic
S. J. Pearton, Xinyi Xia, Fan Ren, Md Abu Jafar Rasel, Sergei Stepanoff, Nahid Al-Mamun, Aman Haque, Douglas E. Wolfe
Summary: Wide bandgap semiconductors SiC and GaN are used in power electronics and light-emitting diodes. They have higher radiation hardness compared to Si devices due to larger threshold energies for creating defects and high rates of defect recombination. However, heavy-ion-induced catastrophic burnout commonly occurs in SiC and GaN power devices. Light-emitting devices are not affected by this mechanism. Strain has also been identified as a parameter affecting radiation susceptibility of wide bandgap devices.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B
(2023)
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)