Abstract
A GaAs-based metal oxide semiconductor field effect transistor (MOSFET) with Al <sub>2</sub> O <sub>3</sub> as gate dielectric was studied. The gate dielectric was grown by atomic layer deposition (ALD). The insertion of a thin In <sub>0.2</sub> Ga <sub>0.8</sub> As layer as part of the channel between the Al <sub>2</sub> O <sub>3</sub> and GaAs channel to improve the interface quality and surface mobility was also investigated. A gate leakage current density less than 10 <sup>-4</sup> A/cm <sup>2</sup> , good transconductance, and a strong accumulation current at V <sub>gs</sub> >0 were exhibited by the depletion-mode MOSFETs.