In-induced (4 × 2) reconstructions of GaAs(001) surfaces

We present first-principles total-energy calculations on In-terminated GaAs(001)(2 × 4) surfaces. The atomic structures and energetics of two structural models suggested from recent experiments are discussed. We favour a surface structure similar to the GaAs(001) β2(4 × 2) surface, where all Ga dimers are replaced by indium. Its stability, however, is limited to In- and As-rich conditions. The surface electronic structure is characterized by filled In sp2-like states energetically close to the bulk valence band edge and empty π-bonding and π*-antibonding combinations of In pz orbitals in the upper half of the GaAs bulk band gap.