Article
Engineering, Electrical & Electronic
Daniel M. Fleetwood, En Xia Zhang, Ronald D. Schrimpf, Sokrates T. Pantelides
Summary: An overview is presented of the effects of displacement damage, total-ionizing dose, and single-event effects in AlGaN/GaN HEMTs. High-fluence proton-induced displacement damage creates defects in the crystal structure. The response of DD/TID is strongly affected by the bias applied during irradiation. GaN-based HEMTs are particularly vulnerable to single-event effects, especially single-event burnout. Significant device-to-device variations in single-event burnout response exist in space systems.
IEEE TRANSACTIONS ON NUCLEAR SCIENCE
(2022)
Article
Materials Science, Multidisciplinary
Xiao Cui, Keyu Ji, Taiping Zhang, Bingjun Wang, Wei Sha, Zilong Dong, Yuanhong Shi, Chunsheng Jiang, Qilin Hua, Weiguo Hu
Summary: This paper investigates the influence of low-fluence neutron irradiation on the electrical properties of AlGaN/GaN HEMTs. The results show that the output performance of the irradiated samples changes similarly, with almost no changes or slight decreases near the knee voltage. As for the leakage current, samples irradiated with different fluences exhibit different characteristics. Simulations using Crosslight software further reveal that low-fluence neutron irradiation primarily affects the 2DEG mobility and surface states of the HEMTs.
ADVANCED MATERIALS TECHNOLOGIES
(2023)
Article
Engineering, Electrical & Electronic
Ashu Wang, Lingyan Zeng, Wen Wang
Summary: In this paper, a methodology of 3D electro-thermo-mechanical simulation is presented to analyze the strain relaxation and self-heating effects of fin AlGaN/GaN high electron mobility transistors (HEMTs). The free boundaries of narrow fins cause strain relaxation of the AlGaN barrier and non-uniform strain distribution near the AlGaN/GaN interface. The strain relaxation leads to a reduction of surface piezoelectric polarization charges (PPCs) and introduces space PPCs in AlGaN/GaN, which decreases the two-dimensional electron gas density and shifts the threshold voltage (V(th)) positively. The simulated V(th) shift with fin width agrees well with experimental results.
SEMICONDUCTOR SCIENCE AND TECHNOLOGY
(2023)
Article
Chemistry, Multidisciplinary
Enrique Maset, Pedro Martin-Holgado, Yolanda Morilla, David Gilabert, Esteban Sanchis-Kilders, Pedro J. Martinez
Summary: This study investigates the effect of gamma irradiation and temperature on the dynamic on-resistance (R-ON) behavior of commercial GaN-on-Si power HEMTs. The results show that gate voltage bias stress contributes to the degradation of dynamic R-ON during irradiation, and temperature accelerates this degradation. Additionally, a partial reduction in dynamic R-ON is observed when the total ionizing dose is around 140 krad(SiO2) and the base temperature during irradiation is not high.
APPLIED SCIENCES-BASEL
(2022)
Article
Engineering, Electrical & Electronic
A. S. Arreola-Pina, J. Mimila-Arroyo
Summary: The study demonstrates that deuterium passivation improves the performance of the AlGaN/GaN High Electron Mobility Transistor (HEMT) and makes it more stable and reliable, despite a certain degree of degradation still occurring at high temperatures.
MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING
(2021)
Article
Engineering, Electrical & Electronic
Hiraku Onodera, Toshiaki Kabemura, Kazushige Horio
Summary: Computer-aided analysis is performed to investigate the impact ionization effects on turn-on characteristics or current collapse of AlGaN/GaN HEMTs. The study reveals that considering impact ionization and higher drain voltage can weaken the current collapse.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2022)
Article
Engineering, Electrical & Electronic
Hiraku Onodera, Toshiaki Kabemura, Kazushige Horio
Summary: The impact of ionization on hard switching in AlGaN/GaN HEMTs is studied. It is found that impact ionization can reduce current collapse and dynamic ON-resistance. In hard switching, the generated holes by impact ionization are trapped, resulting in an increase of positive space charges in the buffer layer, which leads to a smaller current collapse. Additionally, R-DON increases with V-DOFF when it is relatively low, and is higher in hard switching.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Article
Materials Science, Multidisciplinary
X. Cui, K. Ji, L. Liu, W. Sha, B. Wang, N. Xu, Q. Hua, W. Hu
Summary: High electron mobility transistors (HEMTs) based on AlGaN/GaN heterojunctions hold great promise for high-performance power electronics. By introducing high-kappa gate dielectric, such as HfZrOx (HZO), to form MOS-HEMTs, the performance of HEMTs can be enhanced, including higher output performance, lower leakage current, and improved surface properties. Furthermore, the piezotronic effect, which combines piezoelectric and semiconductor properties, offers a novel approach for optimizing HEMTs through external stress. In this study, the dynamic piezotronic effect of AlGaN/GaN HEMTs with HZO gate dielectric is investigated in pulse voltage modes. The results show that applying tensile stress to the GaN layer leads to decreased DC and pulse output characteristics of the MOS-HEMTs, as well as a slight increase in gate leakage current. Theoretical analysis suggests that the applied tensile stress effectively improves the energy band height of the triangular potential well and affects the energy states of defects. This work not only inspires the modulation of device performance using dynamic piezotronic effect, but also expands the potential applications of HEMTs in strain-controlled platforms.
MATERIALS TODAY PHYSICS
(2022)
Article
Physics, Applied
Zhanyong Xing, Haochen Zhang, Yue Sun, Lei Yang, Kunpeng Hu, Kun Liang, Dawei Wang, Houqiang Fu, Haiding Sun
Summary: In this work, an enhancement-mode (E-mode) AlGaN/GaN-based high-electron-mobility transistor (HEMT) with a graded AlGaN cap layer (GACL) is proposed. The GACL is designed to produce high-concentration polarization-induced holes and negative net polarization charges to benefit the normally-OFF operation of the device. The optimized graded-AlGaN-gated metal-semiconductor HEMT achieves a large threshold voltage of 4 V, and shortening the gate length and inserting an oxide layer can suppress gate leakage current and enhance gate voltage swing.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2023)
Article
Computer Science, Information Systems
Ran Ye, Xiaolong Cai, Chenglin Du, Haijun Liu, Yu Zhang, Xiangyang Duan, Jiejie Zhu
Summary: This paper summarizes the investigations of trapping effects and discusses methods to suppress them in AlGaN/GaN HEMTs. Understanding the inner mechanism and comparing different methods can improve the device performance.
Article
Engineering, Electrical & Electronic
Hao Wu, Xiaojun Fu, Jingwei Guo, Tao Liu, Yuan Wang, Jun Luo, Zhiyong Huang, Shengdong Hu
Summary: The research investigated the total ionizing dose and annealing effects on Schottky type p-GaN gate Al0.2Ga0.8N/GaN HEMTs. It was found that the threshold voltage shifts are caused by the accumulation of positive charges at the interface of p-GaN/AlGaN. After performing both high temperature and room temperature annealing processes, the shifted threshold voltage recovered, with high temperature accelerating the recovery process. Experiment results suggest that the total ionizing dose effect is recoverable.
IEEE ELECTRON DEVICE LETTERS
(2022)
Article
Computer Science, Information Systems
Yuchen Li, Sen Huang, Xinhua Wang, Qimeng Jiang, Xinyu Liu
Summary: In this study, the temperature-dependent ON-state breakdown BVON of AlGaN/GaN HEMTs with an AlGaN back barrier was investigated using the gate current extraction technique. It was found that the impact ionization of acceptor-like traps is responsible for the ON-state breakdown in HEMTs when the 2DEG channel is marginally turned on. Additionally, the characteristic electric field of impact ionization was extracted and shown to have a U-shaped temperature dependence.
Article
Physics, Applied
Jun Hyuk Park, Sun-Kyu Hwang, Joonyong Kim, Woochul Jeon, Injun Hwang, Jaejoon Oh, Boram Kim, Younghwan Park, Dong-Chul Shin, Jong-Bong Park, Jongseob Kim
Summary: This study investigates the effect of N2O plasma treatment on the reliability of p-GaN gate AlGaN/GaN HEMTs, specifically in the AlGaN drift region. The results show that N2O plasma treatment can form a GaON/AION compound layer, reduce the number of interface traps, and protect the AIGaN surface, thereby improving the reliability of the device.
APPLIED PHYSICS LETTERS
(2022)
Article
Engineering, Electrical & Electronic
Chunzhou Shi, Ling Yang, Meng Zhang, Mei Wu, Bin Hou, Hao Lu, Fuchun Jia, Fei Guo, Wenliang Liu, Qian Yu, Xiaohua Ma, Yue Hao
Summary: This article demonstrates the superior power performance of a double-channel high-electron-mobility transistor (HEMT) operated at a high drain voltage in the sub-6 GHz range. The double channel with graded barrier HEMT (DCGB-HEMT) shows better direct current characteristics compared to the single channel HEMT (SC-HEMT), including a wider gate voltage swing, higher saturation current, and higher OFF-state breakdown voltage. Through TCAD simulation, it is found that the graded barrier in DCGB-HEMT reduces the peak electric field, resulting in increased breakdown voltage. Furthermore, DCGB-HEMT exhibits improved current collapse and power-added efficiency (PAE) due to better gate control and reduced leakage at high drain voltage.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Article
Engineering, Electrical & Electronic
Khushwant Sehra, Anupama Chanchal, Anupama Anand, Vandana Kumari, Meena Reeta, Mridula Gupta, Meena Mishra, D. S. Rawal, Manoj Saxena
Summary: This study investigates the impact of a ?-shaped gate on the microwave performance of a thin GaN buffer AlGaN/GaN HEMT. A simulation based on an in-house fabricated thin GaN HEMT demonstrates that coupling a ?-shaped gate with a thin GaN buffer improves the reliability of the device. The gate modification enhances the breakdown characteristics and thermal reliability for continuous wave operation, while also improving the pulsed mode operation. This research opens up the possibility of further improving the RF performance of GaN HEMTs by using a ?-shaped gate with a thin GaN buffer to mitigate dispersive trapping effects.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Article
Engineering, Electrical & Electronic
Thomas Weingartner, Mark E. Law
Summary: Accurate and fast Fermi-Dirac integral approximations are used in semiconductor device simulators for carrier concentration calculation. Similar integrals are used for carrier density computation in the subgap region of a superconductor. The difference lies in the density of states (DOS) functional used. Short series approximations, including Gaussian quadrature, are applied to compute the superconductor DOS integral and its Frechet derivatives. Comparisons with numeric integration solutions demonstrate a 600-fold reduction in integration time. A table of short series approximation roots and weights is provided, along with error plots for different temperatures of the niobium pair-breaking potential energy.
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY
(2023)
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
Engineering, Biomedical
Justin Golabek, Matthew Schiefer, Joshua K. Wong, Shreya Saxena, Erin Patrick
Summary: In this study, an artificial neural network (ANN) based predictor was developed to accurately and quickly predict the activation of neural fibers in response to deep brain stimulation (DSB).
JOURNAL OF NEURAL ENGINEERING
(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
Engineering, Electrical & Electronic
Lars Bjorndal, Nimesh Pokhrel, Thomas Weingartner, Polina Leger, Erin Patrick, Mark Law
Summary: Technology Computer Aided Design (TCAD) is being developed for superconductor electronics (SCE) with the inclusion of a model for surface roughness and statistical simulations. The AlOx tunnel barriers used in SCE have thicknesses similar to the surface roughness of sputtered niobium. This unique module is necessary for generating process-simulated structures and electrical simulations of the Nb/Al-AlOx/Nb junction stack.
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY
(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)