Field-dependent degradation mechanisms in GaN-based HEMTs

GaN-based transistors are emerging as almost ideal devices for application in the power conversion field; however, several factors still limit their performance and reliability. This paper reviews the most common field-dependent degradation mechanisms in GaN-based power transistors. Based on the analysis of commercially-available devices we present data on: (i) the recoverable increase in on-resistance due to the exposure to high drain bias, in the off-state; (ii) the permanent degradation of 650 V transistors submitted to off-state step stress with increasing drain bias. The results obtained on commercially-available devices are critically compared to previous papers on the topic, to provide an extensive overview of the physical origin of the degradation.