A model for the critical voltage for electrical degradation of GaN high electron mobility transistors

It has recently been postulated that GaN high electron mobility transistors under high voltage stress degrade as a result of defect formation induced by excessive mechanical stress that is introduced through the inverse piezoelectric effect. This mechanism is characterized by a critical voltage beyond which irreversible degradation takes place. We have built a first-order model for the critical voltage for degradation of GaN HEMTs. In our model, electrical degradation occurs when the elastic energy stored in the AlGaN barrier exceeds a critical value. When using estimations of this critical elastic energy that come from epitaxial studies of strain relaxation in Al-GaN/GaN heterostructures, our proposed model yields predictions for the critical voltage that match experimental observations.