Non-Arrhenius Degradation of AlGaN/GaN HEMTs Grown on Bulk GaN Substrates

The reliability of AlGaN/GaN HEMTs processed on bulk GaN substrates was studied using electrical and optical methods, showing a decreasing degradation with increasing baseplate temperature (T_b). Generation of traps spatially located in both intrinsic and extrinsic HEMT regions was found to be most pronounced for OFF-state bias stress performed at room T_b, while increasing T_b up to 150°C decreased trap generation underneath the gate perimeter. This was attributed to degradation driven by hot electrons as it should dominate over defect-related degradation mechanisms in GaN-on-GaN devices.