Fabrication of gate stack with high gate work function for implantless enhancement-mode GaAs n-channel metal-oxide-semiconductor field effect transistor applications

Abstract

The guidelines for the selection of gate stacks in using an implantless enhancement-mode GaAs n-channel metal-oxide-semiconductor field effect transistor, which is based on a gate material with high work function, are studied using two dimensional device simulation. By employing the silane surface passivation, a high quality gate stack on GaAs substrate comprising of a complementary metal-oxide semiconductor compatible tungsten nitride (WNx) metal gate, which can be easily etched, and a high-permittivity HfAlO gate dielectric is demonstrated. The high work function of 4.97eV and the equivalent oxide thickness of 2.3nm were achieved for this gate stack, which meets the above mentioned normally off operation requirements.