Theoretical study of the Si/GaAs(001)-c(4x4) surface

The deposition of Si on the GaAs(001)-c(4x4) reconstructed surface is studied with the aid of ab initio pseudopotential calculations. With reference to the results of scanning tunneling microscopy (STM), reflectance anisotropy spectroscopy (RAS), and reflection high-energy electron diffraction experiments, models for the Si/GaAs(001)-c(4x4) surface are constructed with Si coverages corresponding to 0.75 and 1.0 ML. STM images an simulated and RAS spectra are calculated for these models and compared with experiment. By examining the local density of states and the magnitude of the optical transition matrix elements it is possible to make a link between the features in the RAS spectra and surface electronic structure. Comments are made on the validity of these surface structural models.