Shulou(Shulou.com)11/24 Report--

CTOnews.com news on December 12, according to the release of China University of Science and Technology, the 68th IEEE International Electron Devices Meeting (IEDM, International Congress of Electronic Devices) was recently held in San Francisco. IEEE IEDM is the annual microelectronics and nanoelectronics academic conference, the world's top forum for reporting on key technological breakthroughs in semiconductor and electronic device technology, design, manufacturing, physics and modeling, along with ISSCC and VLSI, it is also known as the "Olympic event" in the field of integrated circuits and semiconductors. Two research papers on gallium oxide devices (high power gallium oxide Schottky diodes and gallium oxide photodetectors) written by Professor long Shibing of the National exemplary School of Microelectronics of the University of Science and Technology of China were successfully accepted at the conference. This is the first time that the University of Science and Technology of China has published a paper on IEEE IEDM as the first author unit.

High power gallium oxide Schottky diode

How to develop an effective edge terminal structure and alleviate the edge electric field of Schottky electrode is the focus of gallium oxide Schottky diode research. As the gallium oxide P-type doping has not been solved at present, the edge terminal structure related to the PN junction has always been a difficulty. This work is based on the previous research basis of gallium oxide heterostructure PN junction (Weibing Hao, et.al.,in proc. ISPSD), the heterojunction terminal expansion structure (Junction Termination Extension, JTE) has been successfully applied to gallium oxide Schottky diodes. Through reasonable design and optimization of the charge concentration in the JTE region, this study ensures that the forward characteristics of the diode are not affected while maximizing the weakening of the Schottky edge electric field, so as to effectively improve the voltage withstand capacity of the device. The optimized device achieves low on-resistance of 2.9m Ω cm2 and high breakdown voltage of 2.1kV, and its power quality factor is as high as 1.52GW / cm2. In addition, using this optimized process, a large area gallium oxide Schottky diode is successfully fabricated and packaged. The current density of the device is 180A / cm2 at a forward bias voltage of 2V and the reverse breakdown voltage is as high as 1.3kV. The research results were published on IEDM 2022 under the title "High-Performance Vertical β-Ga2O3 Schottky Barrier Diodes Featuring P-NiO JTE with Adjustable Conductivity", and were selected as Top Ranked Student Paper. The first author of the paper is Hao Weibing, a doctoral student in the School of Microelectronics, Professor long Shibing and Xu Guangwei, a special associate researcher in the School of Microelectronics.

Fig. 1 junction terminal extends gallium oxide Schottky diodes. (a) schematic diagram of the device structure. (B) comparison of breakdown characteristics of devices with different charge concentrations in the JTE region. (C) Test circuit for reverse recovery characteristics of packaged devices. (d) performance comparison with reported gallium oxide Schottky diodes. Gallium oxide photodetector

Photodetectors are playing a more and more important role in many fields, such as target tracking, environmental monitoring, optical communication, deep space exploration and so on. Responsiveness and response speed are two key performance parameters of photodetectors. however, there is a restrictive relationship between these two indicators. Due to the lack of mature material defect control technology, this problem is particularly prominent in ultra-wide bandgap semiconductor detectors represented by gallium oxide materials. Professor long Shibing's team alleviates the above constraints by introducing additional auxiliary light sources to achieve directional grating (OPG) regulation (figure 2a). The Ga2O3 / WSe2 junction field effect transistor detector under the OPG scheme shows a negative grating effect (NPG) under the target light (deep ultraviolet), and the threshold voltage of the device moves to the negative direction (Fig. 2B). On the contrary, the auxiliary light source (visible light) radiation makes the device show a positive grating effect (PPG), and the threshold voltage of the device moves to the positive direction. When the target light and auxiliary light are irradiated at the same time, the device integrates the positive and negative opposite grating effect, but the overall performance is that the threshold voltage shifts to the negative direction. The OPG scheme effectively suppresses the serious persistent photoconductive effect in the device, and the response speed of the device is significantly improved (figure 2C). In addition, as shown in figure (2d), the auxiliary visible light introduced in the OPG control scheme has little effect on the key indicators such as light / dark current ratio and responsivity of the device. Finally, when the visible light in the OPG scheme is always on, the response speed is increased by more than 1200 times at the expense of only 10.4% responsiveness, which successfully weakens the constraint between responsiveness and response speed. In particular, when the auxiliary light source is triggered only at the falling edge of the device response through the feedback circuit, the response speed will be improved by an order of magnitude without the sacrifice of responsiveness. In this work, a strategy is proposed that the relationship between responsiveness and response speed can be alleviated by sharing an auxiliary LED with 10 million pixels in the photodetector chip, which has important reference significance for improving the comprehensive performance of the photodetector chip. The research results are published on IEDM 2022 under the title "Alleviating the Responsivity-Speed Dilemma of Photodetectors via Opposite Photogating Engineering with an Auxiliary Light Source beyond the Chip". Professor long Shibing and Zhao Xiaolong, a special associate researcher in the School of Microelectronics of our university, are the co-authors of the paper. Zou Yanni, a doctoral student in the School of Microelectronics, is the first author, and Zeng Yan, a master student, and Tan Pengju, a doctoral student, are co-first authors.

Fig. 2 concept and basic characteristics of opposing grating (OPG) photodetector. CTOnews.com learned that the above two studies were supported by the National Natural Science Foundation of China, the Chinese Academy of Sciences and the Science and Technology Commission of China, as well as the Micro / Nano Research and Manufacturing Center of the University of Science and Technology of China, the Information Science experiment Center of the University of Science and Technology of China, and Fuxin Microelectronics Company in device preparation, simulation and packaging.

IEEE IEDM 2022 meeting official website: https://www.ieee-iedm.org/

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