Design and simulation of GaN/AlGaN HEMTs with low leakage current and high ON/OFF current ratio

A gate-recessed AlGaN/GaN based heterojunction field effect transistor (HFET) on SiC Substrate is designed and simulated using both Si₃N₄ and SiO₂ passivation layers and its DC performance characteristics are analyzed using SENTAURUS TCAD Tools. The maximum ON current of the proposed device is found to be 670mA/mm at a gate voltage of -1.5 V and the maximum OFF current of the device is found to be less than 10^-7 A/μm. This substantially reduced leakage current leads to a high ON/OFF Current ratio. The transconductance of the device is found to be 6e-4S/μm at a gate voltage of 0.5 V. The rise in ON current is mainly due to the increase in the accumulation of the positive charges at the Si₃N₄/GaN interface which leads to the increase in the sheet carrier concentration in the 2DEG channel.