Enhancement of Vth drift for repetitive gate stress pulses due to charge feedback effect in GaN MIS-HEMTs

An unexpected enhancement of Vth drift (ΔVth) in GaN MIS-HEMTs induced by repetitive forward gate bias stress pulses in contrast to single pulses is found. Further, it is revealed that the slope of ΔVth recovery curves decreases for increasing intermediate-recovery time ti, i.e. the recovery time in between individual stress pulses. The observed behavior is explained by the interaction of the 2DEG channel with the dielectric/III-N interface via the III-N barrier during (repetitive) stress, for which a charge feedback mechanism plays a crucial role.