Effect of Hole-Injection on Leakage Degradation in a p-GaN Gate AlGaN/GaN Power Transistor

The gate structure of a p-(Al) GaN gate AlGaN/GaN high electron mobility transistor (HEMT) is a direct bandgap hetero-PN junction, which emits light under forward bias above the threshold voltage. This internal light emission induces persistent photoconductivity (PPC) of the GaN channel/buffer layer, leading to the increase in OFF-state leakage current. In this letter, we studied the OFF-state leakage degradation induced by ON-state gate drive of a p-GaN gate HEMT. Two self-limiting functions are discovered: 1) saturation of the increment of leakage current under continuous pulse operations and 2) dramatically enhanced recovery speed of the internal light-emission-induced PPC effect at elevated temperatures. This letter indicates the robustnessofp-(Al) GaN gate HEMTs in switching applications in spite of the seemingly inevitable leakage current degradation.