Dynamic Interplay of Surface and Buffer Traps in Determining Drain Current Injection induced Device Instability in OFF-state of AlGaN/GaN HEMTs

Through detailed experiments and computations, this study reveals a complex interplay of surface and buffer traps in determining AlGaN/GaN HEMT device's response to an OFF-state drain current injection stress. A time dependent drain voltage build-up is observed in the devices, followed by a gradual reduction for a drain current injection of a few nA. The process of voltage build-up is found to be assisted by channel depletion driven by dynamic trapping in the buffer acceptor traps, while the fall in voltage is caused by channel turn ON driven by trap ionization of the surface donors. Moreover, the current injection induced drain voltage build-up also resulted in a significant increase in the dynamic ON resistance of the device.