Abstract
We have used room temperature photoreflectance spectroscopy to study interfacial electronic properties of various oxide-GaAs heterostructures. The samples, air-, Al 2 O-, Ga 2 O x -, and Ga 2 O 3 (Gd 2 O 3 )-GaAs, were fabricated by in-situ molecular beam epitaxy. Built-in electric fields are 48, 44, and 35 kV/cm for air-, Al 2 O 3 -, and Ga 2 O x -GaAs samples, respectively, corresponding to the interfacial state density (D it ) of 2.4, 2.2, and 1.9×10 11 cm -2 eV -1 , respectively. For the Ga 3 O 3 (Gd 2 O 3 )-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 1×10 11 cm -2 eV -1 . Our results are consistent with the previous data obtained using capacitance-voltage measurements in quasi-static/high frequency modes.