Dynamic gate leakage current of p-GaN Gate AIGaN/GaN HEMT under positive bias Conditions

Among the methods to implement E-mode AIGaN/GaN HEMT, the p-type gate 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 p- GaN region enclosed by two barrier layers, the Schottky barrier and AIGaN barrier, will introduce some problems in normal operation. In the problem we will discuss in this article, for commercial 100 V p-GaN AIGaN/GaN HEMTS, we observe the drift of threshold voltage (V-th) and dynamic change of gate current when the gate is under positive voltage stress. As the voltage and stress time increases, the V-th shifts more to the positive direction, and the change 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.