Atomically smooth Ga2O3(Gd2O3)∕GaAs interface with low interfacial density of states and low electrical leakage currents have been achieved after the heterostructures were air exposed and tailor annealed to ∼750°C. The heat treatments, with annealing at an intermediate temperature of ∼300°C as a necessary step, were carried out under ultrahigh vacuum (UHV) and via standard rapid thermal annealing with flow of pure nitrogen gas. Furthermore, the oxide remains amorphous and minimal interfacial reaction occurred between the oxide and substrate, critical aspects for device performance. Studies using x-ray reflectivity and high-resolution transmission electron microscopy show that the interfacial roughness is <0.2 and <0.4nm for annealing under UHV and non-UHV, respectively. Electrical measurements on the metal-oxide-semiconductor diodes have exhibited low leakage currents (10−8–10−9A∕cm2), a dielectric constant of ⩾14, and a low interfacial density of states (Dit) of <1012cm−2eV−1.
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Chen et al. (2006) studied this question.