Dynamic Breakdown Voltage of GaN Power HEMTs

This work develops a new method to measure the transient breakdown voltage (BV) of a non-avalanche device in ultra-short pulses, based on the unclamped inductive switching (UIS) setup. For the first time, the transient BVs of two types of 600/650-V enhancement-mode p-gate GaN high-electron-mobility transistors (HEMTs) are measured across the pulse duration from 25 ns (dv/dt > 100 V/ns) to 2 s. The BV is found to increase with the decreased pulse width, up to 500 V higher than the static BV. This behavior is explained by the reduced buffer trapping and the resulted lower peak electric field in shorter pulses. Slightly different BV dependences on pulse width are observed in the two types of devices and the mechanisms are unveiled. Repetitive UIS tests are also conducted, revealing that this newly-found "dynamic BV" can provide GaN HEMTs additional overvoltage and surge energy margin in power applications. These findings provide critical new insights on the BV and ruggedness of GaN HEMTs.