Mechanism of Heavy Ion-Induced Leakage Current Increase in Normally-OFF p-GaN Gate HEMTs

The heavy ion-induced leakage current increase is reported for the 650-V p-gallium nitride (GaN) gate HEMTs. The degradation of leakage current increase in GaN HEMTs caused by heavy ions is related to the linear energy transfer (LET) value of the heavy ions and the bias voltage. The increased leakage current is only observed under Ta ion irradiation with an LET value of 60.5 MeV $\cdot $ cm2/mg but not under Kr ion irradiation with an LET value of 20.0 MeV $\cdot $ cm2/mg. Moreover, a higher bias voltage leads to a more pronounced degradation of leakage current increase. When the device is biased at 100 V, heavy ion-induced leakage pathways exist between the drain and source. However, when the voltage is increased to 200 V, in addition to the leakage between the drain and source, leakage pathways form between the drain and gate. Heavy ion-induced damages and morphological changes of the field plate are observed in the irradiated devices, which may contribute to the leakage degradation. The damage mechanism has also been verified through TCAD simulations.