Inversion-type enhancement-mode HfO₂-based GaAs metal-oxide-semiconductor field effect transistors with a thin Ge layer

Using a thin germanium (Ge) interfacial passivation layer (IPL), GaAs HfO₂-based inversion-type enhancement-mode metal-oxide-semiconductor field effect transistors (MOSFETs) are realized. The n-channel MOSFETs on semi-insulating GaAs substrate clearly show surface modulation and excellent current control by gate bias. The threshold voltage of ∼0.5 V, the transconductance of ∼0.25 mS/mm, the subthreshold swing of ∼130 mV/decade, and the drain current of ∼162 μA/mm (normalized to the gate length of 1 μm) at V_d=2 V and V_g=V_th+2 V are obtained. In comparison with previous reports, the dc characteristics of the inversion-type GaAs MOSFETs with a Ge IPL and HfO₂ dielectric demonstrate much similar results.