The effects of MgO gate dielectric thickness and of gate length of MgO/GaN metal-oxide semiconductor field-effect transistors (MOSFETs) were examined using a drift-diffusion model. The saturation drain current scales in an inverse logarithmic fashion with MgO thickness and is <10(-3) A μm(-1) for 0.5 μm gate length devices with oxide thickness >600 Angstrom or for all 1 mum gate length MOSFETs with oxide thickness in the range of >200 Angstrom. The GaN MOSFET shows excellent potential for elevated temperature, high speed applications. (C) 2003 The Electrochemical Society.