GaN-on-Si monolithic bidirectional switch with virtual body to suppress substrate-induced dynamic ON-resistance degradation

Abstract

GaN-on-Si monolithic bidirectional switch (MBDS) enables compact power conversion systems by replacing Si- or SiC-based bidirectional switches composed of two series-connected transistors. However, during the blocking state, a positive substrate potential is generated, leading to severe negative-charge buffer trapping and consequent ON-resistance (RON) deterioration in conventional GaN-on-Si MBDS. In this work, a virtual body GaN-on-Si MBDS is demonstrated to address substrate-induced RON degradation. The virtual body is a hole accumulation layer above the buried AlGaN layer, formed by hole injection from p-GaN gates. Therefore, although severe buffer trapping is triggered by positive substrate potential, the mobile holes in virtual body effectively compensate the negative buffer charges, decoupling the influence of buffer charges on the 2DEG channel. The immunity against substrate-induced degradation is validated by positive back-gating test where the proposed device maintains stable conduction current during substrate stress dynamically switched between 0 and 400 V. As a result, after ±600-V stress, the proposed MBDS exhibits a low dynamic RON/static RON ratio below 1.3, while that of the conventional device exceeds three times that value. Furthermore, in the ±400-V AC chopping test, the proposed device demonstrates reliable chopping operation with 5-kHz gate input. Therefore, the proposed virtual body MBDS demonstrates inherent capability to screen substrate-induced degradation, presenting as a promising solution for next-generation high-performance power conversion system.