Photoreflectance of GaAs/SI-GaAs interface

Photoreflectance spectra of doped molecular-beam-epitaxy GaAs films grown on semi-insulating GaAs substrate, modulated by different pump beams, are studied. From the interference effect of two light beams reflected from different interfaces of a sample, the PR signals from the surface of the MBE film and that from the interface of film and substrate can be distinguished in the spectra. The behavior of the electric fields of the space charge region at the surface of GaAs and the interface of GaAs/SI-GaAs is also investigated.