Reflectance anisotrophy of the GaAs(001) surface

By a combination of theoretical calculations and experiments, we have investigated the GaAs(001) surface and found the reflectance anisotropy (RA) to be extremely sensitive to the atomic configuration upon the surface. By performing a series of ab initio pseudopotential calculations of the optical response of the (2×4) surface reconstruction we find that good agreement with experiment can be obtained when the full relaxation of the surface is taken into account. Experimentally, we show that deposition of as little as 0.01 monolayer of Si modifies the surface structure sufficiently that a significant change in the RA spectrum can be observed