Development and Validation of Repetitive Transient Gate Overvoltage Rating for GaN HEMTs

In this work, time-dependent accelerated gate reliability testing is conducted on GaN high-electron-mobility-transistors (HEMTs), featuring Schottky type pGaN gate. By understanding the underlying failure mechanism, a physics-based lifetime model is developed to project gate lifetime. A 1% duty cycle-based repetitive transient gate overvoltage rating is developed by scaling the projected lifetime at 7 VGS continuous bias to the 10-year expected mission lifespan. To validate the proposed 1% duty cycle factor (DCFactor), an inductive switching circuit is implemented to emulate the transient gate overvoltage ringing that is commonly observed in GaN-based applications. A suite of GaN HEMTs were tested to over one trillion overvoltage pulses with a peak VGS of 7 V at 25°C and 125°C, where neither catastrophic device failure nor significant parameter shifts were found. Not only did the test results confirm the validity of the 1% duty cycle-based repetitive transient overvoltage rating, but it also demonstrated the excellent gate overvoltage robustness of GaN HEMTs.