Electrons, Phonons and Excitons at Semiconductor Surfaces

Abstract

We briefly address’ state-of-the-art’ ab-initio calculations of basic properties of semiconductor surfaces such as their atomic configuration, electronic structure and surface vibrations, as well as, their optical properties and compare exemplary results with experimental data. The surface structure and the electronic ground state are described within the local density approximation (LDA) of density functional theory (DFT). The description of excited electronic states requires to take dynamical correlations in the many electron system into account, which is achieved to a considerable extent within the GW approximation (GWA) leading to the concept of the quasiparticle bandstructure. Surface phonons are treated from first principles within density functional perturbation theory (DFPT). The theory of optical surface properties and surface excitons, in particular, requires to account for the electron-hole Coulomb correlation which is done in the framework of the Bethe-Salpeter equation (BSE). These methods yield results which are in good agreement with experiment and can significantly contribute to an interpretation of experimental data from high-resolution surface microscopy and spectroscopy thus enhancing our current understanding of semiconductor surfaces.