Passivation degradation induced by thermal storage on AlGaN/GaN HEMTs

The effects of thermal storage on GaN-HEMT devices grown on SiC substrate have been investigated by DC, pulsed electrical measurements, and optical microscopy. After 2,000 hours of thermal storage testing at 300°C, only a limited reduction of the DC parameters was observed. Whereas pulsed measurements on aged devices clearly highlight a dramatic current collapse effect that has been attributed to creation of surface traps in the gate-to-drain and gate-to-source access region. A loss of adhesion of the passivation layer was responsible for the observed trap formation. An improved passivation deposition process was therefore developed to prevent passivation detaching.