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 6.7 W/mm power density at 7 GHz. Unpassivated and SiO2-passivated heterostructure field-effect transistors HFETs were also investigated for comparison. Deposited 12 nm thick SiO2 yielded an increase of the sheet carrier density from 7.6 .10^12 to 9.2 .10^12 cm−2 and a subsequent increase of the static drain saturation current from 0.75 to 1.09 A/mm. The small-signal rf characterization of the MOSHFETs showed an extrinsic current gain cutoff frequency fT of 24 GHz and a maximum frequency of oscillation fmax of 40 GHz. The output power of 6.7 W/mm of the MOSHFETs measured at 7 GHz is about two times larger than that of HFETs. The results obtained demonstrate the suitability of GaN-based MOSHFETs for high-power electronics.