Article
Chemistry, Multidisciplinary
Xun Hu, Baiyi Chen, Changfeng Huang, Hongwei Qiu, Na Gao, Yaping Wu, Duanjun Cai, Kai Huang, Junyong Kang, Rong Zhang
Summary: We achieved remarkably enhanced responsivity in metal-semiconductor-metal photodetectors by embedding highly uniform rhodium nanoparticle arrays with large-scale periodicity through localized surface plasmon resonance. Theoretical simulations and experimental results confirmed the improved performance, with a reduced dark current, a shifted maximum responsivity wavelength, and a highly increased enhancement ratio at a specific wavelength. This study contributes significantly to the literature by presenting a novel approach to enhance the performance of AlGaN-based photodetectors in the UV region using a large-scale distributed rhodium nanoparticle array.
Article
Physics, Applied
Junbo Liu, Wensong Zou, Jiawei Chen, Mengyuan Hua, Di Lu, Jun Ma
Summary: This study focused on investigating the transport-limited trapping effects in GaN-on-Si buffer layers and the impact of buffer layer thickness on these effects. The results showed that increasing the buffer layer thickness improved the stability of the device and reduced current collapse. This enhancement was mainly attributed to the reduced vertical electric field within the thickened epitaxy.
APPLIED PHYSICS LETTERS
(2023)
Article
Optics
Aiping Liu, Lei Xu, Xin-Biao Xu, Guang-Jie Chen, Pengfei Zhang, Guo-Yong Xiang, Guang-Can Guo, Qin Wang, Chang-Ling Zou
Summary: Hybrid photon-atom integrated circuits offer great potential for quantum information processing, combining the single-photon nonlinearity and long-lived memory provided by atoms with the passive photonic devices in traditional quantum photonic circuits. This research proposes a stable platform for realizing hybrid photon-atom circuits based on an unsuspended photonic chip, enabling feasible evanescent-field trapping with relatively low laser power.
Article
Chemistry, Analytical
Idriss Abid, Youssef Hamdaoui, Jash Mehta, Joff Derluyn, Farid Medjdoub
Summary: We report on the fabrication and electrical characterization of AlGaN/GaN normally off transistors on silicon designed for high-voltage operation. The normally off configuration was achieved with a p-gallium nitride (p-GaN) cap layer below the gate, enabling a positive threshold voltage higher than +1 V. The buffer structure was based on AlN/GaN superlattices (SLs), delivering a vertical breakdown voltage close to 1.5 kV with a low leakage current all the way to 1200 V.
Article
Engineering, Electrical & Electronic
P. Vigneshwara Raja, Jean-Christophe Nallatamby, Nandita DasGupta, Amitava DasGupta
Summary: This paper presents device simulation studies on static I-V, output-admittance (Y22), and transient characteristics of AlGaN/GaN HEMTs, focusing on surface and buffer trapping effects. By matching simulation results with experimental data, it is possible to identify the trap responsible for specific trapping induced degradation, as well as its concentration and capture cross-section.
SOLID-STATE ELECTRONICS
(2021)
Article
Engineering, Electrical & Electronic
Yutao Cai, Yuanlei Zhang, Ye Liang, Ivona Z. Mitrovic, Huiqing Wen, Wen Liu, Cezhou Zhao
Summary: Novel AlGaN/GaN MIS-HEMTs with a ZrOx charge trapping layer show low ON-state resistance and high breakdown voltage. TCAD simulation results demonstrate the charge trapping and de-trapping behaviors.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2021)
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
Tolen Nelson, Daniel G. Georgiev, Michael R. Hontz, Raghav Khanna, Adrian Ildefonso, Andrew D. Koehler, Karl Hobart, Ani Khachatrian, Dale McMorrow
Summary: The study examines the effect of various trapping centers on single-event transients (SETs) in GaN high-electron-mobility transistors (HEMTs) through calibrated technology computer-aided design (TCAD) simulations. A computational model of a single-channel, Schottky-gate HEMT is developed and validated using static characteristics and single-photon absorption laser data. The simulations reveal a 2-D electron gas (2-DEG) enhancement effect in SETs, resulting in additional collected charge beyond the generated charge. The origins of this effect are investigated, showing an increase in the occupation rate of surface donor traps as charge influx develops in the charge track. Variations in trap characteristics are introduced, and their impact on internal charge collection processes is analyzed. It is further demonstrated that the SET drain current closely follows the transient decay of occupation rate back to the original dc level, indicating the dominance of surface donor traps in the SET response.
IEEE TRANSACTIONS ON NUCLEAR SCIENCE
(2023)
Article
Engineering, Electrical & Electronic
Humaira Zafar, Bruna Paredes, Inas Taha, Juan E. Villegas, Mahmoud Rasras, Mauro F. Pereira
Summary: This paper introduces a broadband and ultra-low crosstalk integrated silicon superlattice waveguide, enabling high-density waveguide integration. The superlattice waveguides are implemented as S-shaped adiabatic bends, which result in ultra-low crosstalks and extremely low insertion loss for the TE polarization. The measurement results show that the average insertion loss for all channels is <= 0.1 dB, and the average crosstalk values for the first and second nearest neighboring waveguides are <= -37.8 dB and <= -45.2 dB, respectively. Simulation results predict efficient broadband performance over a wavelength range of 500 nm, covering all O, E, S, C, L, and U bands. This approach is applicable to other waveguide geometries and integrated photonic platforms.
IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS
(2023)
Article
Engineering, Electrical & Electronic
Gang Lyu, Jin Wei, Wenjie Song, Zheyang Zheng, Li Zhang, Jie Zhang, Sirui Feng, Kevin J. Chen
Summary: This study presents a cost-effective engineered bulk silicon (EBUS) substrate technology, which successfully implements p-n junction on bulk Si substrates. The adverse effects of conventional substrates are eliminated, and the mechanism of crosstalk suppression in the EBUS platform is revealed and verified through tests.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2022)
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
Computer Science, Information Systems
Elodie Carneiro, Stephanie Rennesson, Sebastian Tamariz, Kathia Harrouche, Fabrice Semond, Farid Medjdoub
Summary: Sub-micron-thick AlN/GaN transistors (HEMTs) grown on a silicon substrate for high-frequency power applications were reported. An innovative ultrathin step-graded buffer with a total stack thickness of 450 nm was used, which enabled excellent electron confinement and low leakage current. State-of-the-art GaN-on-silicon power performances were achieved at 40 GHz, with a combination of high power-added efficiency and saturated output power density. This is the first demonstration of high RF performance achieved with sub-micron-thick GaN HEMTs grown on a silicon substrate.
Article
Chemistry, Analytical
Kathia Harrouche, Srisaran Venkatachalam, Lyes Ben-Hammou, Francois Grandpierron, Etienne Okada, Farid Medjdoub
Summary: This paper presents an enhancement of mm-wave power performances using a vertically scaled AlN/GaN heterostructure. The introduction of an AlGaN back barrier underneath a non-intentionally doped GaN channel layer prevents punch-through effects and drain leakage current, while maintaining a moderate carbon concentration in the buffer layer. By carefully tuning the Al concentration in the back barrier layer, the optimized heterostructure provides electron confinement and low trapping effects up to high drain bias for a gate length as short as 100 nm. Load-Pull measurements at 40 GHz showed outstanding performances with a record power-added efficiency of 70% (66%) under high output power density at V-DS = 20 V. These results demonstrate the potential of this approach for future millimeter-wave applications.
Article
Materials Science, Multidisciplinary
Jinli Cao, Shi Wu, Heyu Zhu, Ziran Liu, Yankun Dou, Wen Yang, Chen Huang, Xinfu He
Summary: Adding silicon (Si) and phosphorus (P) to austenitic stainless steel reduces swelling by promoting vacancy diffusion and enhancing recombination rates of vacancy and self-interstitial atoms (SIAs). Si and P have high solubility in Fe and can attract vacancies and SIAs, especially at low temperatures.
COMPUTATIONAL MATERIALS SCIENCE
(2022)
Article
Engineering, Electrical & Electronic
Vipin Joshi, Rajarshi Roy Chaudhuri, Sayak Dutta Gupta, Mayank Shrivastava
Summary: In this study, a computational framework is used to investigate the physical mechanisms of electron trapping in carbon-doped GaN buffer in AlGaN/GaN HEMTs. Device variants with higher lateral electric field exhibit a significant increase in dynamic ON resistance beyond a critical drain stress voltage. Detailed analysis reveals that electron injection and trapping in the C-doped GaN buffer are responsible for the observed dynamic ON resistance behavior. Physical insights into electron injection and trapping behavior are provided through analysis of field evolution, field-enhanced trapping, and its impact on leakage current path within the GaN buffer. The proposed mechanism of field-enhanced electron trapping is validated by computations with device variants having field-independent trapping process and different buffer trap activation energies.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Article
Physics, Applied
Alessandro Caria, Carlo De Santi, Matteo Buffolo, Gaudenzio Meneghesso, Enrico Zanoni, Matteo Meneghini
Summary: The degradation of InGaN-GaN LEDs under high photon densities has been studied, revealing optically-induced processes that decrease internal quantum efficiency. Measurements show a shallow level related to defects which result in an increase in yellow luminescence.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Physics, Applied
Julien Bassaler, Remi Comyn, Catherine Bougerol, Yvon Cordier, Farid Medjdoub, Philippe Ferrandis
Summary: This study focuses on the material investigation of an Al0.9Ga0.1N/GaN heterostructure, identifying various defects in the GaN channel that may contribute to reduced mobility and are linked to the quality of the channel interfaces.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Computer Science, Information Systems
Nicola Trivellin, Davide Fiorimonte, Francesco Piva, Matteo Buffolo, Carlo De Santi, Gaudenzio Meneghesso, Enrico Zanoni, Matteo Meneghini
Summary: This study reports on the reliability of recent commercial UVC LED devices and their efficacy in antiviral technologies for COVID-19. An in-depth analysis of four different state-of-the-art commercial LEDs suitable for disinfection applications indicates limited reliability possibly related to an increase in Shockley-Read-Hall (SRH) recombination. Suggestions for product design improvements will be proposed based on the results of this work.
Article
Chemistry, Analytical
Claudia Casu, Matteo Buffolo, Alessandro Caria, Carlo De Santi, Enrico Zanoni, Gaudenzio Meneghesso, Matteo Meneghini
Summary: This study investigates the defectiveness and degradation mechanisms of InGaN-based quantum wells. By designing a color-coded structure and using numerical simulations, it is found that an increase in traps in the active region is the main cause of degradation. The degradation process consists of two phases, with the first phase occurring in the quantum well closer to the p-contact. The stronger degradation in this well may be due to a lowering of injection efficiency or an increase in SRH recombination.
Article
Physics, Applied
Kathia Harrouche, Srisaran Venkatachalam, Francois Grandpierron, Etienne Okada, Farid Medjdoub
Summary: This article reports on the design optimization of vertically scaled AlN/GaN high electron mobility transistor technology for millimeter-wave applications. The thickness of the undoped GaN channel and the carbon concentration in the buffer were extensively varied and systematically characterized. It was found that a thin GaN channel improves electron confinement but increases trapping effects, especially with shorter gate lengths. Moreover, high carbon concentration in the buffer enables high electron confinement and low leakage current under high electric field, at the expense of trapping effects.
APPLIED PHYSICS EXPRESS
(2022)
Article
Chemistry, Analytical
Idriss Abid, Youssef Hamdaoui, Jash Mehta, Joff Derluyn, Farid Medjdoub
Summary: We report on the fabrication and electrical characterization of AlGaN/GaN normally off transistors on silicon designed for high-voltage operation. The normally off configuration was achieved with a p-gallium nitride (p-GaN) cap layer below the gate, enabling a positive threshold voltage higher than +1 V. The buffer structure was based on AlN/GaN superlattices (SLs), delivering a vertical breakdown voltage close to 1.5 kV with a low leakage current all the way to 1200 V.
Article
Chemistry, Analytical
Kathia Harrouche, Srisaran Venkatachalam, Lyes Ben-Hammou, Francois Grandpierron, Etienne Okada, Farid Medjdoub
Summary: This paper presents an enhancement of mm-wave power performances using a vertically scaled AlN/GaN heterostructure. The introduction of an AlGaN back barrier underneath a non-intentionally doped GaN channel layer prevents punch-through effects and drain leakage current, while maintaining a moderate carbon concentration in the buffer layer. By carefully tuning the Al concentration in the back barrier layer, the optimized heterostructure provides electron confinement and low trapping effects up to high drain bias for a gate length as short as 100 nm. Load-Pull measurements at 40 GHz showed outstanding performances with a record power-added efficiency of 70% (66%) under high output power density at V-DS = 20 V. These results demonstrate the potential of this approach for future millimeter-wave applications.
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
Physics, Applied
Reda Elwaradi, Jash Mehta, Thi Huong Ngo, Maud Nemoz, Catherine Bougerol, Farid Medjdoub, Yvon Cordier
Summary: In this study, two series of AlGaN/GaN/AlN high electron mobility transistor (HEMT) heterostructures were grown using molecular beam epitaxy. The effects of reducing the GaN channel thickness and varying the AlGaN barrier thickness and composition on the structural and electrical properties of the heterostructures were investigated. Material analysis techniques such as high-resolution x-ray diffraction, atomic force microscopy, and cross-sectional transmission electron microscopy were employed. The results showed that reducing the GaN channel thickness led to a decrease in GaN strain relaxation rate, but also caused degradation in crystal quality and electron mobility, along with an increase in sheet resistance. However, a trade-off was observed for a specific HEMT structure with a 50 nm width GaN channel, which exhibited a moderate sheet resistance and a high three-terminal breakdown voltage.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
Zeyu Chi, Tamar Tchelidze, Corinne Sartel, Tsotne Gamsakhurdashvili, Ismail Madaci, Hayate Yamano, Vincent Sallet, Yves Dumont, Amador Perez-Tomas, Farid Medjdoub, Ekaterine Chikoidze
Summary: Spinel zinc gallate ZnGa2O4 is a ternary complex oxide with the widest gap where bipolar conductivity has been demonstrated among emerging ultra-wide bandgap semiconductors. This study used metal organic chemical vapor deposition to grow highly resistive p-type ZnGa2O4 thin films on sapphire and Si substrates to determine its critical electric field and vertical breakdown voltage. The average E-CR was estimated to be at least 5.3 MV cm(-1), which is significantly larger than SiC and GaN.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(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)
Editorial Material
Materials Science, Multidisciplinary
Michael Kneissl, Juergen Christen, Axel Hoffmann, Bo Monemar, Tim Wernicke, Ulrich Schwarz, Asa Haglund, Matteo Meneghini
PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE
(2023)
Article
Computer Science, Information Systems
Elodie Carneiro, Stephanie Rennesson, Sebastian Tamariz, Kathia Harrouche, Fabrice Semond, Farid Medjdoub
Summary: Sub-micron-thick AlN/GaN transistors (HEMTs) grown on a silicon substrate for high-frequency power applications were reported. An innovative ultrathin step-graded buffer with a total stack thickness of 450 nm was used, which enabled excellent electron confinement and low leakage current. State-of-the-art GaN-on-silicon power performances were achieved at 40 GHz, with a combination of high power-added efficiency and saturated output power density. This is the first demonstration of high RF performance achieved with sub-micron-thick GaN HEMTs grown on a silicon substrate.
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.