Investigation of Prolonged Negative Threshold Voltage Shift Induced by Low Drain Bias in Schottky p-GaN Gate HEMTs

초록

In this work, threshold voltage (V-th ) instability was investigated under drain bias stress in Schottky p-GaN gate high electron mobility transistors (HEMTs). A negative shift in threshold voltage was observed under a very low drain bias condition. The negative shift is likely due to an intrinsic donor-like trap state in the p-GaN layer. In contrast, positive shifts in threshold voltage occurred in two distinct phases under higher drain bias stress. With increasing temperature, the initial positive shift was alleviated, while the subsequent positive shift became pronounced during the prolonged stress period. This suggests that multiple mechanisms contribute to the observed positive shifts in threshold voltage. These positive shifts are associated with the Schottky junction barrier and defect state in the GaN buffer layer, respectively.

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