Self-aligned N plus polysilicon-gate GaN MOSFETs

Gallium nitride self-aligned MOSFETs were fabricated using low-pressure chemical vapor deposited silicon dioxide as the gate dielectric and polysilicon as the gate material. Silicon was implanted into an unintentionally-doped GaN layer using the polysilicon gate to define the source and drain regions, with implant activation at 1100degreesC for 5 minutes in nitrogen. The GaN MOSFETs have low gate leakage current, less than 50 pA for circular devices with W/L=800/128 mum. Devices are normally-off with a threshold voltage of 2.7 Volts and a field-effect mobility of 45 cm(2)/V-s at room temperature. The minimum on-resistance measured is 1.9 mOmega-cm(2) with a gate voltage of 34 Volts (W/L=800/2 mum). These devices show that self-aligned MOSFETs are feasible in the III-Nitride system.