Total Ionizing Dose and Annealing Effects on VTH Shift for p-GaN Gate AlGaN/GaN HEMTs

A research of total ionizing dose and annealing effects on Schottky type p-GaN gate Al0.2Ga0.8N/GaN high electron mobility transistors (HEMTs) has been carried out. Devices with breakdown voltages of 100V/200V/650V were irradiated under Co-60 X-rays. Radiation doses reach to a total amount of 500 krad (Si) with dose rate of 50 rad(Si)/s under gate biases of V-GS = 0V/+3V/+5V. Negative threshold voltage shifts were observed, especially under positive gate biases. It is found out that the threshold voltage shifts are due to the accumulation of positive charges (holes) trapped in the interface of p-GaN/AlGaN. Therefore, the shift amount is proportional to the gate bias and the radiation amount, while not related to the breakdown voltage. After the total ionizing dose experiments, both high temperature and room temperature annealing processes were taken. During the annealing processes, the shifted threshold voltage recovered, and high temperature accelerated the recovery process. Experiment results indicate that the total ionizing dose effect is recoverable.