Enhancement mode β-(Al_xGa_1-x)₂O₃/Ga₂O₃heterostructure FET (HFET) with high transconductance and cutoff frequency

This letter reports β-(AlxGa1-x)2O3/Ga2O3 (AlGaO/GaO) heterostructure FETs (HFETs) with significant improvement of peak transconductance (gm), current and power gain cutoff frequencies. A modulation doping scheme is used to form a two dimensional electron gas in AlGaO/GaO heterostructures. Highly scaled transistors (gate lengths of 160-200nm)were fabricatedon thesewafers with source/drain regrowth, scaled source access lengths and Pt Schottky gates. The fabricated HFETs show an enhancement-mode operation with high transconductance and a peak current density of 74 mA/mm. Small signal measurements show a peak current gain cut off frequency (fT) and power gain cutoff frequency (fmax) of 30 and 37 GHz respectively at 10 V drain voltage. While the cutoff frequencies are highest to date, they are limited by high source resistance at the regrowth interface. We observed a moderate off state breakdown at VGS = -2 V, limited by gate leakage and Schottky gate breakdown with an average field strength of 1.35 MV/cm. The fT.LG product 4.8 GHz-μm reported for this device is higher than any other current generation β-Ga2O3 transistors which paves the way for future RF device applications.