High-power SiO2∕AlGaN∕GaN metal-oxide-semiconductor heterostructure field-effect transistors

We report on SiO2∕AlGaN∕GaN metal-oxide-semiconductor heterostructure field-effect transistors (MOSHFETs), which exhibit a 6.7W∕mm power density at 7GHz. Unpassivated and SiO2-passivated heterostructure field-effect transistors (HFETs) were also investigated for comparison. Deposited 12nm thick SiO2 yielded an increase of the sheet carrier density from 7.6×1012to9.2×1012cm−2 and a subsequent increase of the static drain saturation current from 0.75to1.09A∕mm. The small-signal rf characterization of the MOSHFETs showed an extrinsic current gain cutoff frequency fT of 24GHz and a maximum frequency of oscillation fmax of 40GHz. The output power of 6.7W∕mm of the MOSHFETs measured at 7GHz is about two times larger than that of HFETs. The results obtained demonstrate the suitability of GaN-based MOSHFETs for high-power electronics.