Among the methods to implement E-mode AlGaN/GaN HEMT, the p-GaN gate AlGaN/GaN HEMT, which has controllable process and good reliability, has drawn a lot of attention now. A Schottky contact on the p-GaN would further reduce the forward leakage current comparing with the ohmic one. However, the floating p-GaN sandwiched between the gate metal and AlGaN barrier will introduce some problems in normal operation. In this work, for commercial 100 V rating p-GaN AlGaN/GaN HEMTs, we observe the drift of threshold voltage (Vth) and a dynamic change of gate current during forward gate bias stress. As the voltage and stress time increases, the threshold voltage shifts more to the positive direction, and the drift appears to be permanent up to more than 1000 s. On the other hand, a bell shaped gate leakage current with stress time is observed for stress bias larger than 6 V. A model based on dynamic distribution of electron trap during stress is proposed to explain the phenomenon.

p-GaN,E-mode GaN HEMT