Ga2O3(Gd2O3) as a dielectric insulator for GaAs device applications

The novel deposition technique of Ga₂O₃(Gd₂O₃) film by using in-situ molecular beam epitaxy (MBE) has led to the first demonstration of enhancement mode GaAs metal oxide semiconductor field effect transistors. For sub- micron GaAs device applications, the current leakage in the gate dielectric of reduced thickness has been an important issue. In this work, we address this aspect for the Ga₂O₃(Gd₂O₃) thin films deposited on n-type GaAs and present the electrical characteristics of the GaAs MOS structures as a function of the gate dielectric thickness, varying from 16.6 nm to 7.7 nm. The as-deposited thin dielectric layers show, in dark an inversion layer formation as well as an excellent insulator performance: a gate leakage current density as low as 10^-9 A/cm² at low gate bias up to 2.5 V and the electrical breakdown field reaches above 10 MV/cm. The high resolution transmission electron microscopy measurements show a sharp and uniform dielectric/GaAs transition with interfacial roughness < 1 nm.