Degradation characteristics and analysis of AlGaN/GaN high electron mobility transistors under reverse gate bias step stress

In this work, we report on the effects of reverse gate bias step stress on the degradation of AlGaN/GaN high electron mobility transistors (HEMTs), consisting of a decrease in the drain current (I_DS) and an increase in channel resistance (R_on). It was found that these degradations were accompanied with an anomalous decrease of gate current (Ig_off). Interestingly, the nature of the degradation mentioned above was fully reversible and the electroluminescence results obtained by Photo Emission Microscopy (PEM) before and after the stress experiments showed no obvious change. These suggested the degradation under reverse gate bias step stress was not related to the generation of structural defects but the native carrier traps. In addition, it was found that the recovery process of the stressed devices could be easily accelerated by sub-bandgap light illumination which could assist the electron to detrap from traps.