Studies of the interfacial electrical properties of a series of oxide films on GaAs by photoreflectance

This study uses room temperature photoreflectance (PR) to investigate the interfacial characteristics of a series of oxide films, such as Al₂O₃, Ga₂O₃, and Ga₂O₃(Gd₂O₃), on GaAs. The interfacial electric field is derived from the Franz-Kyldysh oscillations (FKOs) in PR spectra measured at various pump beam flux intensities. The electric fields measured from the FKOs are proved to be the maximum fields existing at the interfaces of the samples. Applying the one-side abrupt-junction model of charge distribution, the barrier height across the interface and the density of interfacial states are determined from the square of maximum electric field as a function of pump beam intensity. The interfacial state densities of these oxide-GaAs structures range from 10¹⁰ to 10¹¹ cm^-2. Inside GaAs layer, the charge density is found to be uniformly distributed and is 1×10¹⁶ cm^-3. The electric field within the GaAs layer decreases linearly from its maximum at the interface, to zero, as the distance from the interface increases.