Degradation mechanisms of Schottky p-GaN gate AlGaN/GaN HEMTs under high-temperature reverse bias stress

The degradation mechanisms of Schottky p-GaN gate AlGaN/GaN HEMTs under high-temperature reverse bias (HTRB) stress were investigated and the evolution of the deep traps was identified using deep-level transient spectroscopy. The saturation current of p-GaN gate AlGaN/GaN HEMTs decreased by 18.2% and the threshold voltage shifted positively by 11.6% after the degradation. An electron trap (at 369 K) and a hole trap (at 95 K) were observed in the AlGaN/GaN region, while another hole trap (at 359 K) was found in the p-GaN layer before the stress. Meanwhile, after the stress, the concentration and capture cross section of the hole traps increased in both the p-GaN layer and the AlGaN/GaN region. With regard to the electron trap in the AlGaN/GaN region, the capture cross section increased significantly but the electron trap concentration slightly decreased, which may increase the electron trapping, thereby reducing electrons in the two-dimensional electron gas. These factors result in a positive shift in the threshold voltage and a decrease in the output current. This work provides a new insight into understanding the threshold voltage instability of Schottky p-GaN gate AlGaN/GaN HEMTs.