Evaluation of p-GaN HEMTs degradation under high temperatures forward and reverse gate bias stress

Abstract

In this study, the degradation behavior and physical mechanism of the p-GaN HEMT devices under high-temperature gate bias (HTGB) with +5 V and −5 V were investigated. The DC characteristics show that the device after forward HTGB stress exhibits an obvious negative threshold voltage (Vth ) shift, while the device after reverse HTGB exhibits a negligible shift. The following explanations could be given for the deterioration mechanism: a portion of the two-dimensional hole gas (2DHG) accumulated in the p-GaN layer at the p-GaN/AlGaN interface under long-term forward bias may fill the trap in the AlGaN layer through the tunneling effect. In addition, the drain-source on-resistance of the device had increased after +5 V HTGB stress, and a distinct decrease of accumulated capacitance was observed in the Cg -Vg curve. It indicates a degradation of the gate quality of the device after applying a forward-biased HTGB stress.