Characterization of the interfacial electronic properties of oxide films on GaAs fabricated by in-situ molecular beam epitaxy

We have used room temperature photoreflectance spectroscopy to study interfacial electronic properties of various oxide-GaAs heterostructures. The samples, air-, Al₂O-, Ga₂O _x-, and Ga₂O₃(Gd₂O₃ )-GaAs, were fabricated by in-situ molecular beam epitaxy. Built-in electric fields are 48, 44, and 35 kV/cm for air-, Al₂ O₃-, and Ga₂O_x-GaAs samples, respectively, corresponding to the interfacial state density (D_it ) of 2.4, 2.2, and 1.9×10¹¹ cm^-2 eV ^-1, respectively. For the Ga₃O₃(Gd₂O₃)-GaAs sample, the built-in electric field is negligibly small, indicating a very low interfacial stare density. Estimated by the low field limit criterion, D _it is less than 1×10¹¹ cm^-2 eV ^-1. Our results are consistent with the previous data obtained using capacitance-voltage measurements in quasi-static/high frequency modes