An Investigation of Frequency Dependent Reliability and Failure Mechanism of pGaN Gated GaN HEMTs

This paper presents a frequency dependent reliability study of commercially available GaN HEMTs. Both circuit and device-level experiments were performed to better understand the device-level cause of degradation. It was determined through step-frequency analysis performed in a boost converter that there is a frequency-dependent device degradation for positive gate stress. The point of degradation and its primary effect on the converter before the circuit ultimately failed have been analyzed with converter efficiency, gate current, and gate voltage overshoot. The findings of this experiment clearly show a decline in efficiency and voltage overshoot and increment in gate current, which are linked to device degradation. Furthermore, the recovery behavior of degraded devices has been investigated. However, after initial degradation, devices did not show any signs of recovery over twenty-four-hour recovery periods. The causal origin of these phenomena associated with the gate structure of the device was established by gate step-stress testing as well as an examination and analysis of the possible conduction mechanisms through the gate structure.