Degradation mechanism of static and capacitance characteristics of 700 V p-GaN gate HEMT under repetitive unclamped inductive switching stress

Abstract In this paper, the degradation mechanism of 700 V p-GaN high-electron-mobility transistor subjected to repetitive unclamped inductive switching stress is investigated through a comprehensive analysis of static parameters and capacitance–voltage characteristics. The main reason for the degradation of the threshold voltage ( V _TH ) and early-stage degradation of on-resistance ( R _DS,ON ) is the dynamic competition process between electron and hole trapping in the gate stack. In addition, experimental and simulation results indicate that impact-ionization-generated electrons trapped in the drain-side AlGaN and buffer layers create local negative charges, which repel adjacent channel electrons and widen the depletion region, thereby increasing later-stage R _DS,ON and reducing C _DS . Furthermore, analysis of the gate leakage current ( I _GSS ) reveals that Poole–Frenkel emission is the dominant conduction mechanism under lower positive gate bias, whereas the thermionic emission mechanism prevails under higher bias voltages.