Ga2O3(Gd2O3)was deposited on GaN for use as a gate dielectric in order to fabricate a depletion metal–oxide–semiconductor field-effect transistor (MOSFET). Analysis of the effect of temperature on the device shows that gate leakage is significantly reduced at elevated temperature relative to a conventional metal–semiconductor field-effect transistor fabricated on the same GaN layer. MOSFET device operation in fact improved upon heating to 400&hthinsp;°C. Modeling of the effect of temperature on contact resistance suggests that the improvement is due to a reduction in the parasitic resistances present in the device. ©1998 American Institute of Physics.