Electronic structure and photoemission spectra of thin (GaAs)n(AlAs)n superlattices

Increased translational period of crystalline superlattices gives rise to qualitative modifications of the electron band structure E(k): minigaps appear at new Brillouin zone boundaries and band dispersions are reduced into narrower allowed energy bands. Modifications of the wave functions, consisting in electron confinement into one of the two components of a superlattice can affect the intensities of photoemitted electrons. The layer-resolved contributions from a few topmost layers to the photoelectron intensity are evaluated in the one-step model and the importance of the related optical matrix elements is shown. Large number of surface states and resonances connected with superlattice can be expected. This expectation is confirmed by evaluation of the local densities of electron states for the unreconstructed (1 0 0) surface of the 2×2 superlattice. The space distribution of localized states is presented. Energy distribution curves for normally photoemitted electrons are analyzed from the above viewpoints.