Gate-Recessed AlGaN/GaN MOSHEMTs with the Maximum Oscillation Frequency Exceeding 120 GHz on Sapphire Substrates

Gate-recessed AlGaN/GaN metal-oxide-semiconductor high electron mobility transistors (MOSHEMTs) on sapphire substrates are fabricated.The devices with a gate length of 160nm and a gate periphery of 2 × 75μmexhibit two orders of magnitude reduction in gate leakage current and enhanced off-state breakdown characteristics,compared with conventional HEMTs.Furthermore,the extrinsic transconductance of an MOSHEMT is 237.2mS/mm,only 7% lower than that of Schottky-gate HEMT.An extrinsic current gain cutoff frequency fT of 65 GHz and a maximum oscillation frequency fmax of 123 GHz are deduced from rf small signal measurements.The high fmax demonstrates that gate-recessed MOSHEMTs are of great potential in millimeter wave frequencies.