Worst-Case Bias for High Voltage, Elevated-Temperature Stress of AlGaN/GaN HEMTs

The effects of high-field stress are evaluated for industrial-quality AlGaN/GaN HEMTs as a function of bias and temperature. Positive and negative threshold voltage shifts are observed, depending on stress conditions, indicating the presence of acceptor-like and donor-like traps in these devices. Worst-case transconductance degradation under rated device operating conditions is observed for devices subjected to high-voltage stress in the ON bias condition at elevated temperature. This contrasts with results on earlier-generation devices, which often show worst-case response under semi-ON bias conditions, emphasizing that each technology requires characterization under multiple bias-stress conditions. Neutral and charged oxygen donor-like DX centers and substitutional acceptor-like N
_Ga
centers are the dominant defects contributing to low-frequency noise in these devices. Dehydrogenation of O
_N
-H complexes during O
_N
-bias stress and the resulting increases in densities of O
_N
-related donorlike defects are evidently the reliability-limiting mechanism in these devices.