Degradation mechanism of D-mode GaN HEMT based on high temperature reverse bias stress

Abstract

This paper systematically discusses the degradation of reliability of depleted gallium nitride devices under short to long-term high temperature reverse bias (HTRB) stress. The electrical parameters of the device during the whole process were obtained by the stress-measure-stress alternation experimental scheme. We believe that the Schottky barrier decreases and the channel conduction resistance increases in the process of high temperature and high field stress. This conclusion can be verified by the gate-lag characteristics. It is a new phenomenon that capacitor degradation can be divided into three stages in the experiment. Further analysis shows that the device has three processes: dielectric layer consumption-AlGaNlGaN layer interface donor state increase-AlGaN barrier layer degradation FN emission and trap-assisted tunneling. There is also a positive correlation between capacitance and gate leakage. When the channel is rapidly depleted, the capacitance decreases gradually and the leakage reaches saturation. Current saturation is mainly because the external voltage has little effect on the longitudinal electric field between Schottky electrode and Ohm electrode, but has a great effect on the transverse electric field. The conclusion of this paper will be of reference significance to the manufacturing process and the life of the device under normal operation.