V_th and R_on Instability of GaN Power HEMTs with pGaN Gate Under Negative Gate Bias

We investigate the impact of negative gate stress on the stability of threshold voltage and on-resistance of p-GaN gate power HEMTs. We demonstrate three different trapping processes and describe the related kinetics: (process 1), trapping of electrons at the AlGaN/GaN barrier, induced by the positive gate voltage used to monitor the threshold voltage during stress; (process 2), de-trapping of electrons from donor states, with consequent negative shift in the threshold voltage; (process 3) slow electron trapping in the dielectric/semiconductor interfaces. Reverse gate leakage current was modeled in temperature to understand the physical origin of process 3. The results reported in this paper are of relevance for the stability of p-GaN gate power HEMTs in several real-life applications.