Electronic structure of the GaAs(001)2x4 and GaAs(110) surfaces studied by high-resolution electron-energy-loss spectroscopy

We compare, by high-resolution electron-energy-loss spectroscopy (HREELS), the electronic structure of the GaAs(110)1x1 surface and that of the GaAs(001)2x4 As-rich surface in the energy-loss region 0.5-5 eV. The HREEL spectra are interpreted in terms of realistic calculations. The spectral features above the gap are assigned to electronic transitions involving surface and/or bulk states. Losses at energies within the gap are associated to defect states at the surface. [S0163-1829(98)51236-2].