Degradation of GaN high-electron mobility transistors in voltage step stress

Voltage step-stress tests on GaN-on-SiC HEMT showed that electric field is a driving factor for degradation. The position of localized damage is corresponding to the high electric field region. A degradation mode different from previous reports is observed, which led to an increase of drain current after stress in certain conditions. We attribute this to the collection of the positive mobile charge under the gate during the stress.