Simulation design of a high-breakdown-voltage p-GaN-gate GaN HEMT with a hybrid AlGaN buffer layer for power electronics applications

摘要

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 Al_aGa_(1-a)N zone and an Al_bGa_(1-b)N 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 cm~2), and a high Baliga's figure of merit (4.47 GW/cm~2) are obtained at the same time with an L_(gd) (gate-to-drain distance) of 6 μm, a distance from the gate to the Al_aGa_(1-a)N/Al_bGa_(1-b)N 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.