Local-field effects in reflectance anisotropy spectra of the (001) surfaceof gallium arsenide

Characteristic reflectance anisotropy spectra of the naturally oxidized (00 1) surfaces of GaAs undoped crystals and Ga0.7Al0.3As epitaxial films are m easured in the energy range 1.5-5.7 eV. The spectra are interpreted in the framework of the microscopic model proposed for a GaAs(001)/oxide interface and the reflectance anisotropy (difference) theory developed for a multila yer medium with a monolayer of atomic dipoles located near one of the inter faces. The anisotropy of dipole polarizability and the anisotropy of the pl ane lattice formed by dipoles are taken into account within the unified Gre en function approach of classical electrodynamics. A good agreement between the measured and calculated reflectance anisotropy spectra of the oxidized GaAs(001) surfaces shows that the local field effects at the semiconductor -oxide interface make the main contribution to these spectra. (C) 2001 MAIK "Nauka/Interperiodica".