Article
Engineering, Electrical & Electronic
Ming Xiao, Yifan Wang, Ruizhe Zhang, Qihao Song, Matthew Porter, Eric Carlson, Kai Cheng, Khai Ngo, Yuhao Zhang
Summary: This study presents a novel junction termination extension (JTE) technique with a graded charge profile for vertical GaN p-n diodes. The fabrication process does not require GaN etching and only involves a single-step implantation. The fabricated GaN p-n diodes exhibit high breakdown voltage and robust avalanche current density, making them suitable for various vertical GaN devices.
IEEE ELECTRON DEVICE LETTERS
(2023)
Article
Engineering, Electrical & Electronic
Jingcun Liu, Ruizhe Zhang, Ming Xiao, Subhash Pidaparthi, Hao Cui, Andrew Edwards, Lek Baubutr, Cliff Drowley, Yuhao Zhang
Summary: This letter presents the avalanche and surge current ruggedness of the industry's first 1.2-kV-class vertical GaN p-n diodes on 100-mm GaN substrates. The diodes exhibit a critical avalanche energy density and surge energy density, as well as small reverse recovery and fast switching capabilities, highlighting the high ruggedness of GaN p-n junctions.
IEEE TRANSACTIONS ON POWER ELECTRONICS
(2021)
Article
Engineering, Electrical & Electronic
Tolen Nelson, Prakash Pandey, Daniel G. Georgiev, Michael R. Hontz, Andrew D. Koehler, Karl D. Hobart, Travis J. Anderson, Adrian Ildefonso, Raghav Khanna
Summary: This work examines a new hybrid edge termination structure for vertical GaN diodes. The hybrid structure consists of superimposed guard rings onto a junction termination extension, resulting in zones with alternating implantation depths. By optimizing the geometry design, it achieves a high breakdown voltage response while minimizing computational cost.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2022)
Article
Engineering, Electrical & Electronic
Luke Yates, Brendan P. Gunning, Mary H. Crawford, Jeffrey Steinfeldt, Michael L. Smith, Vincent M. Abate, Jeramy R. Dickerson, Andrew M. Armstrong, Andrew Binder, Andrew A. Allerman, Robert J. Kaplar
Summary: This article details the growth and fabrication methods for developing large-area vertical GaN p-n diodes, which have gained significant interest for their high-voltage blocking and high-power efficiency capabilities. Experimental results show that these diodes exhibit high breakdown voltage and low on-resistance.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2022)
Article
Engineering, Electrical & Electronic
Houqiang Fu, Kai Fu, Srabanti Chowdhury, Tomas Palacios, Yuji Zhao
Summary: This comprehensive review discusses the recent progress in vertical GaN power devices, focusing on device design principles and fabrication processes. It covers basic structures, fabrication processes, and device physics, including materials and device engineering aspects. Key topics such as avalanche breakdown and leakage mechanisms are also discussed, providing valuable information for researchers and inspiring future interdisciplinary collaborations.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2021)
Article
Engineering, Electrical & Electronic
Takuya Maeda, Tetsuo Narita, Shinji Yamada, Tetsu Kachi, Tsunenobu Kimoto, Masahiro Horita, Jun Suda
Summary: Breakdown characteristics of homoepitaxial GaN p-n junction diodes with p(+)-n and p-n(+) junctions with relatively heavy doping concentrations are systematically investigated. The results show consistent behavior with numerical simulations using impact ionization coefficients (IICs) in GaN.
IEEE ELECTRON DEVICE LETTERS
(2022)
Article
Engineering, Electrical & Electronic
Jingcun Liu, Ming Xiao, Ruizhe Zhang, Subhash Pidaparthi, Hao Cui, Andrew Edwards, Michael Craven, Lek Baubutr, Cliff Drowley, Yuhao Zhang
Summary: This work investigates the high-temperature performance and avalanche capability of normally-off 1.2-K V-CLASS vertical gallium nitride (GaN) fin-channel junction field-effect transistors (Fin-JFETs), demonstrating their superior thermal stability, gate leakage current mechanism, and high-bias drain leakage current. The results show a BVAVA over 1700 V and a critical avalanche energy (E-AVA) of 7.44 J/cm(2), indicating the great potentials of vertical GaN Fin-JFETs for medium-voltage power electronics applications.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2021)
Article
Engineering, Electrical & Electronic
Feng Zhou, Weizong Xu, Fangfang Ren, Dong Zhou, Dunjun Chen, Rong Zhang, Youdou Zheng, Tinggang Zhu, Hai Lu
Summary: Through selective Mg-ion implantation technology, GaN JBS diode achieved significantly enhanced avalanche ruggedness and surge current capability for highly reliable power operation, demonstrating excellent electrostatic performances, zero reverse recovery behaviors, crucial avalanche capability, and a large safe-operation-area under both forward and reverse inductive spikes even under extreme switching conditions.
IEEE TRANSACTIONS ON POWER ELECTRONICS
(2021)
Article
Chemistry, Multidisciplinary
Zhigang Li, Jiteng Li, Weike Wang, Qijie Yan, Yongrui Zhou, Luping Zhu, Bingqiang Cao, Bingqing Wei
Summary: The discovery of super-semiconductors based on metallic bi-layer shell arrays provides an opportunity to achieve ultra-low-power consumption semiconductor devices. For example, p-n junction diodes based on super-semiconducting nanostructured Ag/Al arrays have achieved near zero-threshold voltage and low power consumption. The high breakdown field of these diodes allows access to ultra-low-power semiconducting transistors, integrated circuits, chips, etc.
ADVANCED MATERIALS
(2023)
Article
Engineering, Electrical & Electronic
Prakash Pandey, Tolen M. Nelson, William M. Collings, Michael R. Hontz, Daniel G. Georgiev, Andrew D. Koehler, Travis J. Anderson, James C. Gallagher, Geoffrey M. Foster, Alan Jacobs, Mona A. Ebrish, Brendan P. Gunning, Robert J. Kaplar, Karl D. Hobart, Raghav Khanna
Summary: A simple edge termination structure for a GaN p-n diode is proposed, which has been empirically validated to increase breakdown capability. This technique reduces complexity in manufacturing and improves the device's voltage-blocking ability.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2022)
Article
Engineering, Electrical & Electronic
Xuan Liu, Maojun Wang, Jin Wei, Cheng P. Wen, Bing Xie, Yilong Hao, Xuelin Yang, Bo Shen
Summary: Utilizing hydrogen plasma treatment and controlled diffusion, a junction termination extension (JTE) structure with gradient hole density (GHD) is spontaneously formed for vertical gallium nitride (GaN) p-n diode based on selective area partial passivation of Mg acceptors with hydrogen. The reverse bias for the quasi-vertical GaN-on-Si p-n diodes to reach a leakage current of 1 A/cm(2) was boosted from 631 to 1100 V. Additionally, the fabricated diode exhibited superior rectifying behavior with an ON/OFF-current ratio of 10(12) and a specific differential ON-resistance of 0.75 m omega middot cm(2).
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Article
Physics, Applied
Tomoyuki Shoji, Tetsuo Narita, Yoshitaka Nagasato, Masakazu Kanechika, Takeshi Kondo, Tsutomu Uesugi, Kazuyoshi Tomita, Satoshi Ikeda, Tomohiko Mori, Satoshi Yamaguchi, Yasuji Kimoto, Jun Kojima, Jun Suda
Summary: This study investigated the reverse leakage currents in GaN p-n junctions nearly free of dislocations. It was found that diodes with breakdown voltages (BVs) ranging from 130 to 1000 V exhibited avalanche breakdown at the designed voltages, with significant leakage currents observed at reverse bias values far below the BVs. The data were explained based on direct band-to-band tunneling (BTBT), with BTBT current dominant in devices with lower BVs and far below detection limit in devices with higher BVs.
APPLIED PHYSICS EXPRESS
(2021)
Article
Engineering, Electrical & Electronic
Luca Nela, Catherine Erine, Amirmohammad Miran Zadeh, Elison Matioli
Summary: Researchers have proposed a simple and robust platform for intrinsic polarization super junctions (i-PSJs) that enables excellent charge matching for a wide range of structures without doping. They identified surface donor states as the cause of charge mismatch and provided a strategy to minimize their impact. They also extended this concept to multichannel i-PSJ structures, greatly improving the device performance.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2022)
Article
Physics, Applied
Maciej Matys, Kazuki Kitagawa, Tetsuo Narita, Tsutomu Uesugi, Jun Suda, Tetsu Kachi
Summary: Vertical GaN junction barrier Schottky (JBS) diodes with superior electrical characteristics and nondestructive breakdown were realized using selective-area p-type doping via Mg ion implantation and subsequent ultra-high-pressure annealing. The JBS diodes exhibited record low on-resistance and high breakdown, along with low reverse leakage current and high current density, making them strong candidates for low loss power switching applications.
APPLIED PHYSICS LETTERS
(2022)
Article
Chemistry, Multidisciplinary
Artem Shushanian, Daisuke Iida, Zhe Zhuang, Yu Han, Kazuhiro Ohkawa
Summary: In this study, we investigated the wet electrochemical etching of n-GaN films in oxalic acid. By observing microphotographs and analyzing product data, we revealed the electrochemical oxidation mechanism of n-GaN in oxalic acid and the formation of porous structures.
Article
Engineering, Electrical & Electronic
Marco Nicoletto, Alessandro Caria, Carlo De Santi, Matteo Buffolo, Xuanqui Huang, Houqiang Fu, Hong Chen, Yuji Zhao, Gaudenzio Meneghesso, Enrico Zanoni, Matteo Meneghini
Summary: In this article, we extensively investigate the degradation of gallium nitride (GaN)-based high periodicity indium GaN (InGaN)-GaN multiple quantum well (MQW) solar cells under optical stress at high excitation intensity and high temperature. The obtained results suggest that the degradation originates from the diffusion of hydrogen, and the proposed analytical methodology provides insight into MQW solar cell degradation.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Article
Physics, Applied
Micah S. S. Haseman, Daram N. N. Ramdin, Wenshen Li, Kazuki Nomoto, Debdeep Jena, Huili Grace Xing, Leonard J. J. Brillson
Summary: This study investigates the movement of electrically charged defects in Ga2O3 vertical trench power diodes using cathodoluminescence point spectra and hyperspectral imaging. The researchers observed the spatial rearrangement of optically active defects under strong reverse bias. These findings demonstrate the potential impact of extreme electric fields on atomic rearrangement and local doping changes in beta-Ga2O3, highlighting the importance of nanoscale device geometry in other high-power semiconductor devices.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
F. Piva, M. Pilati, M. Buffolo, N. Roccato, N. Susilo, D. Hauer Vidal, A. Muhin, L. Sulmoni, T. Wernicke, M. Kneissl, C. De Santi, G. Meneghesso, E. Zanoni, M. Meneghini
Summary: This paper investigates the degradation of deep-ultraviolet LEDs and provides new insights through the combination of C-DLTS, electro-optical characterization, and simulations. The C-DLTS measurements identify three traps, two of which are associated with Mg-related defects also detected in the unaged device, and one related to point defects generated during the ageing procedure. Furthermore, the forward I-V variation is explained by the degradation of the p-contact due to Mg passivation based on the obtained results and TCAD simulations. The optical degradation is attributed to the increase in defectiveness in the active region and surrounding areas, leading to a decrease in injection efficiency, an increase in non-radiative recombination, and an increase in trap-assisted tunneling processes.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
Jashan Singhal, Eungkyun Kim, Austin Hickman, Reet Chaudhuri, Yongjin Cho, Huili Grace Xing, Debdeep Jena
Summary: We conducted a study on the compositional dependence of electrical characteristics in AlxGa1-xN quantum well channel-based AlN/AlGaN/AlN high electron mobility transistors (HEMTs), with x values of 0.25, 0.44, and 0.58. The use of selectively regrown n-type GaN Ohmic contacts resulted in increased contact resistance with higher Al content in the channel. The DC HEMT device characteristics showed a progressive reduction in maximum drain current densities and a simultaneous decrease in threshold voltage with increasing x values.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
F. Piva, M. Grigoletto, R. Brescancin, C. De Santi, M. Buffolo, J. Ruschel, J. Glaab, D. Hauer Vidal, M. Guttmann, J. Rass, S. Einfeldt, N. Susilo, T. Wernicke, M. Kneissl, G. Meneghesso, E. Zanoni, M. Meneghini
Summary: We investigated the impact of Mg-doping on the performance and degradation kinetics of AlGaN-based UV-C LEDs. Higher Mg-doping in the electron-blocking layer (EBL) resulted in higher optical power at low current levels due to increased hole injection efficiency. The reduction of optical power followed a non-exponential trend and could be explained by the generation/activation of defects within the quantum wells. Higher Mg-doping in the EBL mitigated the degradation rate, potentially due to the presence and movement of hydrogen reducing the de-hydrogenation rate of point defects in the active region.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
Eungkyun Kim, Zexuan Zhang, Jimy Encomendero, Jashan Singhal, Kazuki Nomoto, Austin Hickman, Cheng Wang, Patrick Fay, Masato Toita, Debdeep Jena, Huili Grace Xing
Summary: Recent observations of high density polarization-induced electron gases in ultra-thin N-polar GaN layers on single-crystal AlN have allowed for the development of N-polar high electron mobility transistors (HEMTs) on AlN. These devices can take advantage of AlN's thermal and power handling capabilities, while also benefitting from N-polar structures like a strong back barrier. Experimental demonstrations of N-polar GaN/AlGaN/AlN HEMTs on single-crystal AlN substrates have shown promising performance, paving the way for RF electronics with excellent thermal management based on N-polar single-crystal AlN.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
Nicola Roccato, Francesco Piva, Carlo De Santi, Matteo Buffolo, Manuel Fregolent, Marco Pilati, Norman Susilo, Daniel Hauer Vidal, Anton Muhin, Luca Sulmoni, Tim Wernicke, Michael Kneissl, Gaudenzio Meneghesso, Enrico Zanoni, Matteo Meneghini
Summary: The long-term stability of AlGaN-based UVC LEDs is crucial for various applications. In this study, the degradation of these LEDs was analyzed and the variation of electrical characteristics was modeled using 2D simulations based on results from deep-level optical spectroscopy. The increase in forward leakage current during aging was attributed to an increase in trap-assisted tunneling. The degradation kinetics analysis suggests a defect diffusion process, possibly involving impurities from the p-type layers.
APPLIED PHYSICS LETTERS
(2023)
Article
Engineering, Electrical & Electronic
Wenwen Zhao, Mohammad Javad Asadi, Lei Li, Reet Chaudhuri, Kazuki Nomoto, Huili Grace Xing, James C. M. Hwang, Debdeep Jena
Summary: This study demonstrates epitaxial AlN thin-film bulk acoustic resonators (FBARs) on SiC substrates with first-order thickness extensional modes of 15-17 GHz. The achieved quality factor Q(max) of approximately 443, electromechanical coupling coefficient k(eff)(2) of approximately 2.3%, and f center dot Q of approximately 6.65 THz figure of merit are among the highest in the Ku-band (12-18 GHz). The clean primary mode with a high quality factor allows these epitaxial AlN FBARs to be used in Ku-band acoustic filters with clean bands and steep rejection. Additionally, their compatibility with AlN/GaN/AlN quantum well high-electron-mobility transistors (QW HEMTs) allows for monolithic integration with HEMT low noise amplifiers (LNAs) and power amplifiers (PAs).
IEEE ELECTRON DEVICE LETTERS
(2023)
Article
Engineering, Electrical & Electronic
Gao Zhan, Fabiana Rampazzo, Carlo De Santi, Mirko Fornasier, Gaudenzio Meneghesso, Matteo Meneghini, Herve Blanck, Jan Gruenenpuett, Daniel Sommer, Ding Yuan Chen, Kai-Hsin Wen, Jr-Tai Chen, Enrico Zanoni
Summary: DC characteristics of AlGaN/GaN HEMTs with different thickness values of the undoped GaN channel layer were compared. An abnormal transconductance (gm) overshoot accompanied by a negative threshold voltage (V-TH) shift was observed during IDS-V-GS sweep in devices with thinner GaN layer. At the same time, a non-monotonic increase in gate current was observed. In OFF-state, electron trapping occurs in the undoped GaN layer or at the GaN/AlN interface, leading to a positive VTH shift. When the device is turning on at a sufficiently high V-DS, electron de-trapping occurs due to trap impact-ionization; consequently, V-TH and therefore ID suddenly recovers, leading to the gm overshoot effect. These effects are attributed to electron trap impact-ionization and consequent modulation of the device's electric field.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Article
Materials Science, Coatings & Films
Thomas J. Smart, Felix V. E. Hensling, Dong Yeong Kim, Lena N. Majer, Y. Eren Suyolcu, Dominik Dereh, Darrell G. Schlom, Debdeep Jena, Jochen Mannhart, Wolfgang Braun
Summary: This work investigates the behavior of aluminum sources in oxide thermal laser epitaxy and identifies two distinct operating regimes. At high laser-beam fluences, the source emits reproducible fluxes independent of oxygen pressure. At lower beam fluences, the flux increases with increasing oxygen pressure due to suboxide formation. The study demonstrates reproducible rate control over a wide range and highlights the advantages of thermal laser epitaxy over oxide molecular-beam epitaxy in handling aluminum sources.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2023)
Article
Materials Science, Multidisciplinary
Nicola Trivellin, Francesco Piva, Davide Fiorimonte, Matteo Buffolo, Carlo De Santi, Enrico Zanoni, Gaudenzio Meneghesso, Matteo Meneghini
Summary: This study reports on the reliability of commercial ultraviolet-C (UV-C) light-emitting diodes (LEDs) under constant current stress. Electrical, optical, and spectral analyses were conducted on UV-C LEDs with a peak emission at 275 nm and a nominal power of 12 mW at 100 mA. Degradation tests were performed at maximum rated current, double the maximum, and three times the maximum. The results show that LED lifetime is inversely proportional to the stress current density, potentially due to high-energy electrons from Auger-Meitner recombination.
PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE
(2023)
Article
Engineering, Electrical & Electronic
Michele Zenari, Matteo Buffolo, Mirko Fornasier, Carlo De Santi, Jeroen Goyvaerts, Alexander Grabowski, Johan Gustavsson, Sulakshna Kumari, Andim Stassren, Roel Baets, Anders Larsson, Gunther Roelkens, Gaudenzio Meneghesso, Enrico Zanoni, Matteo Meneghini
Summary: This study investigates the optical degradation of VCSILs designed for operation at 845 nm in PICs. The degradation is related to impurity diffusion, which affects device characteristics in different ways depending on the migration region. Understanding the root cause of physical degradation is crucial for improving the lifetime of these novel optical sources.
IEEE JOURNAL OF QUANTUM ELECTRONICS
(2023)
Article
Engineering, Electrical & Electronic
Alessandro Caria, Carlo De Santi, Matteo Buffolo, Marco Nicoletto, Xuanqi Huang, Houqiang Fu, Hong Chen, Yuji Zhao, Gaudenzio Meneghesso, Enrico Zanoni, Matteo Meneghini
Summary: The aim of this article is to investigate the degradation mechanisms of GaN solar cells under harsh conditions, specifically forward current stress. The results indicate that the main parameters of the cells decrease under this stress, and there is a correlation between the charge distribution inside the active region and the concentration of trap states. The decrease in power conversion efficiency is attributed to a redistribution of charge in the active region, resulting in an increase in midgap states density. These findings fill the gap in the literature regarding the long-term reliability of GaN solar cells under harsh conditions.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Article
Engineering, Electrical & Electronic
Nicola Modolo, Carlo De Santi, Giulio Baratella, Andrea Minetto, Luca Sayadi, Sebastien Sicre, Gerhard Prechtl, Gaudenzio Meneghesso, Enrico Zanoni, Matteo Meneghini
Summary: Ideally, the emission profile in semiconductors should follow a pure exponential decay, but complex devices often exhibit a strongly stretched exponential shape. Conventional methodologies for mapping capture/emission time constants may lead to inaccuracies. In this article, a new methodology based on the double inverse Laplace transform is introduced to accurately extract the capture-emission time map of defects. The proposed approach is compared with conventional approximations, providing insight into the accuracy of simplified methods. The method is tested on custom-generated functions and successfully applied to extract the capture/emission time map from a power GaN HEMT subjected to positive bias instability test.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Article
Computer Science, Information Systems
Alexander Herzog, Simon Benkner, Babak Zandi, Matteo Buffolo, Willem D. Van Driel, Matteo Meneghini, Tran Quoc Khanh
Summary: This study reports on the degradation mechanisms and dynamics of silicone encapsulated high-power ultraviolet A (UV-A) light-emitting diodes (LEDs) with a peak wavelength of 365 nm. Stress tests were conducted for 8665 hours at forward currents ranging from 350 mA to 700 mA and junction temperatures up to 132 degrees C. The results showed a significant decrease in optical power, with faster degradation at higher operating conditions. The degradation mechanisms were analyzed, and a degradation model was proposed to estimate the device lifetime under different operating parameters. Additional stress test data was used to validate the accuracy of the model's lifetime predictions.
