AES and PYS studies of the polar GaAs(111) as surface after thermal cleaning in ultrahigh vacuum

Auger Electron Spectroscopy (AES) and Photoemission Yield Spectroscopy (PYS) have been used in the investigations of elemental composition and electronic properties of the polar GaAs-(111) As surface after thermal cleaning by electron bombardment heating at 770 K in an ultrahigh vacuum of 10^-7 Pa. The surface concentration of As was 0.01 ML which corresponds to the (1 × 1) and weak (3 × 3) atomic structure, whereas the work function and absolute band bending were 4.05 ± 0.02 eV and -0.21 ± 0.04 eV, respectively. Moreover, two filled electronic surface state bands localized in the band gap below the Fermi level EF and in the upper part of the valence band were observed which have been described as the dangling-bond surface state and back-bond surface state bands, respectively.