Electron surface states in short-period superlattices: (GaAs)2/(AlAs)2(100)-c(4×4)

The electronic structure of (GaAs)2/(AlAs)2(1 0 0)-c(4 × 4) superlattice surfaces was studied by means of angular-resolved photoelectron spectroscopy (ARUPS) in the photon energy range 20–38 eV. Four samples with different surface termination layers were grown and As-capped by molecular beam epitaxy (MBE). ARUPS measurements were performed on decapped samples with perfect c(4 × 4) reconstructed surfaces. An intensive surface state was, for the first time, observed below the top of the valence band. This surface state was found to shift with superlattices’ different surface termination in agreement with theoretical predictions.