Depletion mode GaAs metal–oxide–semiconductor field effect transistors with Ga2O3(Gd2O3) as the gate oxide

We have successfully fabricated depletion mode GaAs metal–oxide–semiconductor field effect transistors using Ga2O3(Gd2O3) as the gate oxide and an oxygen implant isolation technique. Growth of the device structure including the deposition of Ga2O3(Gd2O3) was performed in a multichamber molecular beam epitaxy system. A 1 μm×100 μm device shows excellent dc and microwave characteristics with low output conductance. Complete pinchoff at Vg=−2.5 V and operation in the accumulation mode of up to Vg=2.5 V were measured. The maximum transconductance was 100 mS/mm, with a high drain current density of 315 mA/mm. Microwave testing yielded a fT of 14 GHz and a fmax of 35 GHz.