Article
Engineering, Electrical & Electronic
Jun-Hyeok Lee, Jeong-Gil Kim, Hee-Sung Kang, Jung-Hee Lee
Summary: In this study, effective reduction of interface states and current collapse in AlGaN/GaN MISHFETs was demonstrated by using Al2O3 and in-situ AlN passivation layer. The results showed that the Al2O3/in-situ AlN double passivation layer is highly effective in suppressing current collapse and improving device performance. This indicates that the double passivation layer method is promising for the fabrication of high-performance AlGaN/GaN MISHFETs.
SOLID-STATE ELECTRONICS
(2021)
Article
Physics, Applied
Xin Chen, Yaozong Zhong, Shumeng Yan, Xiaolu Guo, Hongwei Gao, Xiujian Sun, Haodong Wang, Fangqing Li, Yu Zhou, Meixin Feng, Ercan Yilmaz, Qian Sun, Hui Yang
Summary: The characteristics of an AlGaN/GaN high-electron-mobility transistor buffer structure are studied and optimized by employing an AlN/GaN superlattice (SL) structure. The influence of buffer traps on carrier transport behaviors and electrical performance for SL buffer structures under a high electric field is analyzed. The AlN/GaN SL buffer structures are further optimized with various AlN/GaN thickness ratios and their total thickness, achieving a high breakdown voltage and suppressing the buffer trapping effect.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2023)
Article
Chemistry, Multidisciplinary
Kuan-Chang Chang, Xibei Feng, Huangbai Liu, Kai Liu, Xinnan Lin, Lei Li
Summary: This study proposes an effective and accurate computational-fitting method for extracting the mobility of GaN HEMT. The method involves measuring the total resistance between source and drain at different gate voltages and fitting the total resistance with respect to the overdrive voltage to determine the carrier mobility and the non-gate resistance.
Article
Nanoscience & Nanotechnology
Jung-Hui Tsai, Jing-Shiuan Niu, Xin-Yi Huang, Wen-Chau Liu
Summary: This article compares the electrical characteristics of Al0.28Ga0.72N/AlN/GaN MOS-HEMT with a 20-nm-thick Al2O3 layer and the conventional MS-HEMT. Results show that with the insertion of the Al2O3 layer, the MOS-HEMT exhibits a 9% increase in maximum transconductance and a significant reduction of gate leakage current by about five orders of magnitude.
SCIENCE OF ADVANCED MATERIALS
(2021)
Article
Physics, Applied
Hanghai Du, Zhihong Liu, Lu Hao, Guangjie Gao, Weichuan Xing, Weihang Zhang, Yachao Zhang, Hong Zhou, Shenglei Zhao, Jincheng Zhang, Yue Hao
Summary: In this study, sub-60 mV/dec subthreshold swings (SS) were achieved in GaN-based metal-insulator-semiconductor high electron mobility transistors (MISHEMTs). The SS values remained consistent regardless of the direction of the gate bias sweep. The observed physical mechanisms responsible for the small SS include capture and emission of electrons in traps.
APPLIED PHYSICS LETTERS
(2023)
Article
Engineering, Electrical & Electronic
Shuang Liu, Weihang Zhang, Jincheng Zhang, Xiufeng Song, Yinhe Wu, Dazheng Chen, Shengrui Xu, Shenglei Zhao, Yue Hao
Summary: A high-electron-mobility transistor (HEMT) with AlN/GaN superlattice (SL) channel has been successfully demonstrated on a silicon substrate, achieving high performance with optimized breakdown voltage and output current. The trap states in the AlN/GaN SL channel were investigated, revealing a reduction in trap state density in the parasitic channel and specific energy levels in the main channel. This study represents a significant advancement in the development of SL channel HEMTs on cost-effective silicon substrates and provides a novel technology for high output current in AlGaN multichannel devices.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2021)
Article
Engineering, Electrical & Electronic
Jingyu Shen, Chao Yang, Liang Jing, Jingwei Guo, Ping Li, Hao Wu, Shengdong Hu
Summary: In this study, an enhancement mode p-GaN gate HEMT with selective regrowth and strain engineering has been proposed. The device shows improved 2DEG density and surface electric field distribution, leading to significant improvements in ON-resistance and breakdown voltage.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Article
Computer Science, Information Systems
Yanxu Zhu, Xiaomeng Song, Jianwei Li, Jinheng Li, Baoliang Fei, Peiyang Li, Fajun Li
Summary: In this paper, a novel ring-gate structure AlGaN/GaN HEMT device is proposed and its performance is improved through optimization designs. By changing the electrode structure and device size parameters, the drain current and threshold voltage are successfully enhanced, and better output characteristics are achieved.
Article
Chemistry, Physical
Dmitri S. S. Arteev, Alexei V. V. Sakharov, Wsevolod V. V. Lundin, Evgenii E. E. Zavarin, Andrey E. E. Nikolaev, Andrey F. F. Tsatsulnikov, Viktor M. M. Ustinov
Summary: This study investigates the influence of Fe segregation on the electrical properties of two-dimensional electron gas in AlGaN/AlN/GaN heterostructures. It was found that the concentration and mobility of the electron gas decrease with thinner channel layer thickness, leading to an increase in sheet resistance. The drop in mobility is attributed to a combination of ionized impurity scattering and various scattering effects.
Article
Engineering, Electrical & Electronic
Chia-Hao Liu, Hsien-Chin Chiu, Hsiang-Chun Wang, Hsuan-Ling Kao, Chong-Rong Huang
Summary: The study shows that DJ-HEMT exhibits higher gate voltage swing in the gate region due to the dual junction, enhancing gate performance. Compared to ST-HEMT, DJ-HEMT has higher V-TH, saturation current, I-ON/I-OFF ratio, and gate swing voltage. In addition, DJ-HEMT also has lower leakage current and longer lifetime measurement.
IEEE ELECTRON DEVICE LETTERS
(2021)
Article
Engineering, Electrical & Electronic
Yan Cheng, Yat Hon Ng, Zheyang Zheng, Kevin J. Chen
Summary: Enhancement-mode (E-mode) submicron 0.45-μm p-GaN gate HEMTs on 200-mm high-resistivity-Si (HRS) substrates have been demonstrated with high uniformity and high overall combined performance for RF applications. The p-GaN gate HEMT exhibits positive threshold voltage, high transconductance, and high saturation current density. It also shows low OFF state leakage current, high breakdown voltage, and high cut-off frequencies. Additionally, it achieves high power output and efficiency at 5 GHz.
IEEE ELECTRON DEVICE LETTERS
(2023)
Article
Engineering, Electrical & Electronic
Binxing Li, Guoqiang Zhang, Chengrui Li, Gaolin Wang, Shaobo Liu, Dianguo Xu
Summary: This article proposes a novel negative voltage self-recovery gate drive (NVSRGD) to suppress crosstalk in gallium nitride (GaN) based bridge configuration. By using a resistor-capacitor-diode voltage divider, a negative gate-source voltage is established to suppress positive crosstalk. In addition, an antiparallel diode is added to create a low-impedance Miller current path, working together with the self-recovery gate-source voltage to suppress negative crosstalk. The effectiveness of this method is verified through double-pulse testing based on GS66508B.
IEEE TRANSACTIONS ON POWER ELECTRONICS
(2022)
Article
Engineering, Electrical & Electronic
Kai Liu, Runhao Wang, Chong Wang, Xuefeng Zheng, Xiaohua Ma, Junchun Bai, Bin Cheng, Ruiyu Liu, Ang Li, Yaopeng Zhao, Yue Hao
Summary: This paper investigates the influence of a lightly doped p-GaN cap layer on p-GaN/AlGaN/GaN high electron mobility transistors (HEMTs). The results show that the p(-)-GaN cap layer optimizes the gate characteristics, significantly reduces the gate leakage voltage, and increases the gate forward breakdown voltage and continuous operating voltage. Furthermore, simulation results demonstrate that the p(-)-GaN cap layer disperses the electric field and alleviates the electric peak, thereby suppressing impact ionization and carrier injection.
SEMICONDUCTOR SCIENCE AND TECHNOLOGY
(2022)
Article
Engineering, Electrical & Electronic
Deepthi Cingu, Xiangdong Li, Benoit Bakeroot, Nooshin Amirifar, Karen Geens, Kristof J. P. Jacobs, Ming Zhao, Shuzhen You, Guido Groeseneken, Stefaan Decoutere
Summary: This study provides a comprehensive evaluation of the reliability of 200V HEMTs in reverse conduction mode, revealing that p-GaN gate HEMTs exhibit high reliability in reverse conduction, which can simplify the design of synchronous power systems.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2021)
Article
Engineering, Electrical & Electronic
Hao Yu, Alireza Alian, Uthayasankaran Peralagu, Ming Zhao, Niamh Waldron, Bertrand Parvais, Nadine Collaert
Summary: The density of AlGaN surface states was extracted and analyzed, showing the influence of AlN thickness on 2DEG density and AlGaN surface potential. The accuracy and factors affecting the DSS extraction method were demonstrated.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2021)
Article
Multidisciplinary Sciences
Vikrant J. Gokhale, Brian P. Downey, D. Scott Katzer, Neeraj Nepal, Andrew C. Lang, Rhonda M. Stroud, David J. Meyer
NATURE COMMUNICATIONS
(2020)
Article
Physics, Applied
E. N. Jin, A. C. Lang, M. T. Hardy, N. Nepal, D. S. Katzer, D. F. Storm, B. P. Downey, D. J. Meyer
JOURNAL OF APPLIED PHYSICS
(2020)
Article
Physics, Applied
Vikrant J. Gokhale, Brian P. Downey, D. Scott Katzer, David J. Meyer
APPLIED PHYSICS LETTERS
(2020)
Article
Nanoscience & Nanotechnology
Andrew C. Lang, D. Scott Katzer, Neeraj Nepal, David J. Meyer, Rhonda M. Stroud
Summary: Epitaxial transition metal nitrides (TMNs) are a new class of crystalline thin film metals that can be integrated with common group III-nitride semiconductors. This study used high-resolution transmission electron microscopy to identify different phases of tantalum nitrides with N-sublattice ordering, revealing Ta-deficient films with specific planar defects. These findings lay the foundation for the application of this epitaxial TMN material in new electronic and superconducting device structures.
ACS APPLIED MATERIALS & INTERFACES
(2021)
Article
Multidisciplinary Sciences
Phillip Dang, Guru Khalsa, Celesta S. Chang, D. Scott Katzer, Neeraj Nepal, Brian P. Downey, Virginia D. Wheeler, Alexey Sus, Andy Xie, Edward Beam, Yu Cao, Cathy Lee, David A. Muller, Huili Grace Xing, David J. Meyer, Debdeep Jena
Summary: Researchers have successfully observed the integer quantum Hall effect in a two-dimensional electron gas by combining high critical temperature nitride superconductors with nitride semiconductor heterostructures of metal polarity.
Article
Acoustics
Vikrant J. Gokhale, Brian P. Downey, Jason A. Roussos, D. Scott Katzer, David J. Meyer
Summary: This report demonstrates the first passive RF comb filters made using epi-HBAR technology, with multiple sharp filter passbands suitable for high-power RF operation, and potential to replace larger off-chip or discrete-component comb filters.
IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL
(2021)
Article
Nanoscience & Nanotechnology
Eric N. Jin, Brian P. Downey, Vikrant J. Gokhale, Jason A. Roussos, Matthew T. Hardy, Tyler A. Growden, Neeraj Nepal, D. Scott Katzer, Jeffrey P. Calame, David J. Meyer
Summary: The epitaxial integration of high dielectric constant Sr1-xCaxTiO3 films onto AlGaN/GaN/4H-SiC structures has shown promising results in improving electric field management and device breakdown voltage without significant impact on channel transport properties. The films exhibit minimal hysteresis, high dielectric constant, and reduced leakage compared to Schottky contacted samples, indicating their potential for enhancing functionality and performance in high-power RF and power-switching applications.
Article
Physics, Applied
Diego Vaca, Matthew Barry, Luke Yates, Neeraj Nepal, D. Scott Katzer, Brian P. Downey, Virginia Wheeler, Luke Nyakiti, David J. Meyer, Samuel Graham, Satish Kumar
Summary: In this study, we investigate the lower thermal conductivity of beta-Ga2O3 thin films grown by MBE. We compare experimental results with numerical predictions and find that the presence of boundary scattering and defects significantly affect the thermal conductivity of the thin films. By considering various types of defects in the calculations, we identify that crystals with gallium vacancies and stacking faults exhibit thermal conductivities closer to the experimental values. These findings provide insights for improving the thermal conductivity of MBE-grown samples.
APPLIED PHYSICS LETTERS
(2022)
Article
Engineering, Electrical & Electronic
Vikrant J. Gokhale, Matthew T. Hardy, D. Scott Katzer, Brian P. Downey
Summary: This letter presents the first demonstration of epitaxial scandium aluminum nitride (ScAlN) based high-overtone bulk acoustic resonators (epi-HBARs) with over 1600 acoustic cavity resonance modes spanning the X - Ka bands (8 GHz - 40 GHz). Key metrics for the ScAlN epi-HBARs include Q > 7000, fxQ > 10(14) Hz, and k(eff)(2) xQ(BVD) > 0.22 at cryogenic temperatures for frequencies as high as 40 GHz (>500, >6 x 10(12) Hz, >0.1 at room temperature). Such robust RF MEMS epi-HBARs with piezoelectric drive and readout are promising candidates for compact microwave/millimeter wave signal processing elements.
IEEE ELECTRON DEVICE LETTERS
(2023)
Article
Engineering, Electrical & Electronic
Brian P. Downey, Shawn Mack, Andy Xie, D. Scott Katzer, Andrew C. Lang, James G. Champlain, Yu Cao, Neeraj Nepal, Tyler A. Growden, Vikrant J. Gokhale, Matthew T. Hardy, Edward Beam, Cathy Lee, David J. Meyer
Summary: In this study, the micro-transfer printing technique is used to integrate two solid-state RF device technologies, GaN and GaAs high-electron-mobility transistors, on the same interposer. The devices are released from their growth substrate using an epitaxial sacrificial layer, and a thin polymer adhesion layer is used to ensure a strong bond with the target substrate. The results show that the device/interposer interface has no voids, and the polymer adhesion layer has a thickness of 5+/-2 nm. There is no significant degradation in dc electrical characteristics after device transfer for either device technology. The ability to combine different solid-state technologies at the device level with high density offers a promising approach for meeting the demands of next-generation RF and mixed-signal circuits.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Article
Materials Science, Coatings & Films
Neeraj Nepal, D. Scott Katzer, Andrew C. Lang, Brian P. Downey, Matthew T. Hardy, David J. Meyer
Summary: Tantalum nitride (γ-Ta2N) thin films were grown on 3 in. diameter 6H- or 4H-SiC substrates by radiofrequency plasma molecular beam epitaxy (MBE). The MBE grown layers showed epitaxial characteristics and nearly pure γ-Ta2N phase. The lattice parameters and strain of the films on SiC were measured. Additionally, the MBE growth of AlN/γ-Ta2N /SiC heterostructures was demonstrated.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2023)
Article
Acoustics
Vikrant J. Gokhale, Albrecht Jander, Brian P. Downey, Pallavi Dhagat, Shawn C. Mack, D. Scott Katzer, Jason A. Roussos, David J. Meyer
Summary: This study presents a detailed characterization and analysis of magnetoelastic high-overtone bulk acoustic resonators (ME-HBARs) operating in the S-band. These devices are fabricated by microtransfer printing piezoelectric GaN transducers onto a ferrimagnetic YIG substrate. The experiment demonstrates the hybridization of phonons and magnons in YIG, allowing for the suppression or tuning of acoustic modes in the ME-HBAR. The ME-HBARs can be used as dynamically tunable or switchable resonators, oscillators, comb filters, and frequency selective limiters in RF signal processing subcomponents.
IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL
(2023)
Article
Physics, Applied
Eric N. Jin, Andrew C. Lang, Brian P. Downey, Vikrant J. Gokhale, Matthew T. Hardy, Neeraj Nepal, D. Scott Katzer, Virginia D. Wheeler
Summary: This work demonstrates the growth of SrTiO3 thin films on high-electron-mobility transistor heterostructures based on an emergent ultra-wide bandgap (UWBG) semiconductor ScAlN, and investigates the effects of pre-growth chemical treatments on the heterostructure properties. It is found that among the treatments studied, the solvent and sulfuric-phosphoric acid cleans have the least disruptive effects on the electrical properties of the GaN channel, while the sulfuric-phosphoric acid clean results in the best oxide crystallinity. The transmission electron microscopy imaging reveals that intermixing occurs at the oxide-nitride interfaces for both samples, but the sample treated with sulfuric-phosphoric acid has lower interface roughness and larger STO grain size.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
Matthew T. Hardy, Andrew C. Lang, Eric N. Jin, Neeraj Nepal, Brian P. Downey, Vikrant J. Gokhale, D. Scott Katzer, Virginia D. Wheeler
Summary: This work investigates the role of nucleation layer, growth temperature, and strain management in maximizing the material properties of high ScN fraction ScxAl1-xN on SiC substrates. The study finds that optimizing these factors can improve the crystal quality and defect density of ScxAl1-xN material, making it suitable for applications in RF resonators, filters, and ferroelectric devices.
JOURNAL OF APPLIED PHYSICS
(2023)
Proceedings Paper
Engineering, Electrical & Electronic
Vikrant J. Gokhale, Brian P. Downey, D. Scott Katzer, David J. Meyer
Summary: This study investigates the phonon diffraction limited performance of GaN/AIN/NbN/SiC epitaxial HBARs and explores the tradeoffs in using them compared to confocal HBARs with curved engineered surfaces. The smallest epi-HBARs achieve high performance near the diffraction limit at 7.2K, while larger devices not limited by diffraction exhibit even higher performance.
2021 34TH IEEE INTERNATIONAL CONFERENCE ON MICRO ELECTRO MECHANICAL SYSTEMS (MEMS 2021)
(2021)