Analysis on degradation mechanisms of normally-off p-GaN gate AlGaN/GaN high-electron mobility transistor

The degradation mechanisms of enhancement-mode p-GaN gate AlGaN/GaN high-electron mobility transistor was analyzed extensively, by means of drain voltage stress and gate bias stress. The results indicate that: (i) High constant drain voltage stress has only a negligible impact on the device electrical parameters, with a slightly first increase and then decrease in output current; (ii) A negative shift of threshold voltage and increased output current were observed in the device subjected to forward gate bias stress, which is mainly ascribed to the hole-trapping induced by high electric field across the p-GaN/AlGaN interface; (iii) The analyzed device showed an excellent behavior at reverse gate bias stress, with almost unaltered threshold voltage, output current, and gate leakage current, exhibiting a large gate swing in the negative direction. The results are meaningful and valuable in directing the process optimization towards a high voltage and high reliable enhanced AlGaN/GaN high-electron mobility transistor.