Simulation design of a high-breakdown-voltage p -GaN-gate GaN HEMT with a hybrid AlGaN buffer layer for power electronic
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Simulation design of a high‑breakdown‑voltage p‑GaN‑gate GaN HEMT with a hybrid AlGaN buffer layer for power electronics applications Yong Liu1 · Qi Yu1 · Jiangfeng Du1
© Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract We propose a novel GaN high-breakdown-voltage high-electron-mobility transistor (HB-HEMT) with a p-GaN gate and hybrid AlGaN buffer to improve the breakdown voltage and Baliga’s figure of merit. The hybrid AlGaN buffer is composed of a horizontally arranged AlaGa1−aN zone and an AlbGa1−bN zone, each having different Al compositions a and b. The proposed HB-HEMT is simulated using the Silvaco technology computer-aided design (TCAD) tool ATLAS, considering the polarization model, low-field mobility, high-field mobility, and Selberherr’s impact ionization model to simulate the direct-current (DC), breakdown, and C–V properties of the proposed HB-HEMT. The breakdown voltage of the HB-HEMT is significantly improved by introducing the hybrid AlGaN buffer structure, which can effectively modulate the electric field distributions within the channel and the buffer. A high breakdown voltage (1450 V), a low specific on-state resistance (0.47 mΩ cm2), and a high Baliga’s figure of merit (4.47 GW/cm2) are obtained at the same time with an Lgd (gate-to-drain distance) of 6 µm, a distance from the gate to the A laGa1−aN/AlbGa1−bN interface of 4 µm, and Al compositions of a = 0.25 and b = 0.1. The simulated C–V results also reveal that the GaN HB-HEMT shows better switching characteristics than the conventional GaN HEMT with a p-GaN gate. Keywords GaN · HEMT · Hybrid AlGaN buffer · On-state resistance · Breakdown voltage
1 Introduction Gallium nitride (GaN) high-electron-mobility transistors (HEMTs) have been widely researched owing to their good properties such as high electron mobility, high electron saturation velocity, and high breakdown voltage (BV) [1–4]. Due to their higher critical breakdown electric field and higher current driving capability, GaN HEMTs are more attractive than silicon-based devices for use in power electronics applications [5, 6]. Recently, normally-off GaN HEMTs have been widely studied for fail-safe operation and simpler drive circuits [7, 8], and several methods to implement normallyoff GaN HEMTs, such as trench gate structures [9, 10], thin barriers [11, 12], and fluorine implantation [13, 14], have
* Jiangfeng Du [email protected] 1
State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, China
been proposed. The use of a p-gate is a popular recent technique applied in normally-off GaN HEMTs [15–18], and several high-breakdown-voltage GaN HEMTs with p-GaN gate structures have been reported [19, 20]. To the best of the authors’ knowledge, the highest average breakdown electric field and figure of merit (FOM) for p-GaN gate GaN HEMTs are 1.4 MV/cm and 3.9 GW/cm2, respectively [19], far below the critical breakdown electric field of GaN (3 MV/cm). Similar to convent
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