Abstract
Built-in electric fields and interfacial state densities (D it ) in a series of oxide-GaAs heterostructures fabricated by in situ molecular beam epitaxy were studied using room temperature photoreflectance. The samples investigated were air-, Al 2 O 3 -Ga 2 O x -, and Ga 2 O 3 (Gd 2 O 3 )-GaAs. We found that the built-in electric fields are 48, 44, and 38 kV/cm for air-, Al 2 O 3 -, and Ga 2 O x -GaAs samples, respectively. For the Ga 2 O 3 (Gd 2 O 3 )-GaAs sample, the built-in electric field is negligibly small, indicating a very low interfacial state density. Estimated by the low field limit criterion, D it is less than 1 × 10 11 cm -2 eV -1 . Our results on the Ga 2 O 3 (Gd 2 O 3 )-GaAs sample are consistent with the data obtained previously using capacitance-voltage measurements in quasistatic/high frequency modes and photoluminescence measurements. © 1998 American Institute of Physics.