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 base-plate 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
$^{\circ}\hbox{C}$
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.