A first principles metal-semiconductor interaction study: Aluminum   adsorption on Ga-rich GaAs(100)-(2x1) and beta(4x2) surfaces
  Ab initio self-consistent total energy calculations using second order Moller-Plesset perturbation theory and Hay-Wadt effective core potentials with associated basis sets (HWECP's) for gallium and arsenic have been used to investigate the chemisorption properties of atomic aluminum on the Ga-rich GaAs(100)-(2x1) and beta(4x2) surfaces. Finite sized hydrogen saturated clusters with the experimental zinc-blende lattice constant of 5.654 ang. and the energy optimized Ga dimer bond length of 2.758 ang. have been used to model the semiconductor surface. To investigate the effects of the core electrons of aluminum in the adsorption process, we have represented the Al adatom with both HWECP's and an all electron 6-311++G** basis set. Detailed energetics of chemisorption on the (100) surface layer including adsorption beneath the surface layer at an interstitial site are investigated. Mulliken population analysis and highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps are reported for all considered sites of chemisorption. 
Michael L. Mayo (1) and Asok K. Ray (1) ((1) Physics Department, The   University of Texas at Arlington, Arlington, Texas)