INTERFERENCE EFFECTS IN PHOTOREFLECTANCE OF EPITAXIAL LAYERS GROWN ONSEMIINSULATING SUBSTRATES

Interferences were observed in the photoreflectance spectra of homoepi taxial layers grown on semi-insulating GaAs and InP substrates. The mo dulation mechanism responsible for the interference effect was studied from the frequency and temperature dependence of the interference amp litude and the effect of continuous wave illumination. The results are in agreement with the model that the modulation is due to electrons d rifting to the interface from the surface. A simple model was used to fit the interference spectra to the Lorentzian wave forms from the sub strate and the epitaxial layer.