Electro-optic effects in the optical anisotropies of (001) GaAs

Abstract

We report on both optical reflectance anisotropy and electro- reflectance measurements carried out in order to determine the physical origin of the impurity-dependent anisotropy observed in the reflectance spectrum of (001) GaAs. We found that such anisotropy is actually a bulk related, linear electro-optic effect produced by the electric field present at the semiconductor surface. This electric field is due to the pinning of the Fermi level at this surface because of the presence of surface states. Our results are important for the application of optical reflectance anisotropy measurements to the study of surface processes in zinc-blende semiconductors.