Gate-Current-Dominated Positive Threshold Voltage Shift Under PBTI Stress in Schottky p-GaN Gate HEMTs

While positive bias temperature instability (PBTI)-induced threshold voltage (V${}_{\text {th}}\text {)}$instability is a major bottleneck in gallium nitride (GaN) power electronics, the role of gate current remains poorly understood and is often confounded by temperature effects. In this work, the role of gate current in threshold voltage instability is investigated using short-term PBTI stress to isolate the positive shift component before the counteracting component becomes pronounced. The positive shift decreases with increasing gate current, even at the same temperature. Moreover, nearly identical positive shifts are observed at different temperatures when the gate current is comparable. These results suggest that the positive shift is not determined by temperature alone but is associated with gate current. C–V and recovery analyses suggest that this current-dependent positive shift is associated with electron trapping. Arrhenius analysis of the secondary recovery transient of the positive shift yields an activation energy of 174 meV, suggesting trap states associated with the p-GaN/AlGaN interface.