RF Performance of N-Polar AlGaN/GaN MIS-HEMTs Grown by MOCVD on Sapphire Substrate

We present a high-performance nitrogen-polar AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistor grown on sapphire substrate using metal-organic chemical vapor deposition. Source-terminated field plates were used to mitigate the electric field in the drain-extension region and reduce DC-to-RF dispersion. Devices with 0.7-mum gate length showed a current-gain cutoff frequency (
f

_T
) of 14 GHz and a power-gain cutoff frequency (
f

_max
) of 36 GHz. A continuous-wave output power density of 4.7 W/mm was measured at 4 GHz, with an associated power-added efficiency of 64% and a large-signal gain of 14.4 dB at a drain bias of 30 V.