Total-Ionizing-Dose Radiation Effect on Dynamic Threshold Voltage in p-GaN Gate HEMTs

In this article, total-ionizing-dose (TID) response for dynamic threshold voltage (V-TH) in p-GaN gate high electron mobility transistors (HEMTs) is studied. A nonmonotonic dependence of V-TH on dynamic gate stress is observed and the impact mechanism of Irradiation damages in the metal/p-GaN/AlGaN system is revealed. At the p-GaN/AlGaN interface, the new interface traps built by irradiation cause more positive V-TH shift. At the metal/p-GaN Schottky junction, irradiation damage related to possible nitrogen vacancies would enhance the hole-injection with increasing gate current. The hole-injection enhancement gives rise to stronger optical pumping and more holes trapped in the AlGaN barrier, causing more negative V-TH shift. Irradiation damages would change the competition relationship between electron trapping and the hole-injection, which is responsible for the nonmonotonic V-TH shift. The increase of gate current, drain leakage, and change of gate capacitance is presented to verify the mechanism.