Local-field effects in reflectance anisotropy spectra of oxidized (001) GaAs and AlGaAs surfaces

Oxidized (001) surfaces of both GaAs crystals and Ga0.7Al0.3As alloys are found to exhibit characteristic reflectance anisotropy (RA) spectra in the range 1.5–5.5 eV. A microstructure model of GaAs/oxide interface is proposed to treat the observed spectra within a quasi-microscopic theory of reflectance anisotropy developed for multilayer dielectric arrangements. Quantitative agreement between measured and calculated RA spectra shows the principal spectral features to be related to local-field effects at the GaAs/oxide interface, which is typical of A3B5 compounds.