Degradation processes in AlGaN/GaN HEMTs under high drain-bias off-state stress

This paper reports on degradation processes in the AlGaN/GaN HEMTs under high drain-bias off-state stress. The devices were off-stressed at the drain voltage of 60 V and the gate voltage of -5 V for 30 min, resp.60 min. Static device performance was evaluated before, during and after the stress. Performed measurements show a slight degradation in the drain current and a decrease of the threshold voltage. However, these effects are partially recovered as follows from the measurement performed 30 min after the stress. All these indicates that the electrons that accumulate in the structure as well as on the surface of AlGaN layer create an electrostatic charge induced by high electric field between gate and drain. This causes a reduction in the channel current and plays a major role during the off-state degradation of AlGaN/GaN HEMTs.