A theoretical investigation of migration potentials of ga adatoms near kink and step edges on GaAs(001)-(2x4) surface

Migration potentials of Ga adatoms near kink and step edges are qualitatively investigated using empirical interatomic potential and an energy term. The energy term, as a function of the number of electrons remaining in the Ga dangling bond, is extracted from ab initio pseudopotential calculations. The calculated results imply that the lattice sites in the missing dimer row are favorable for Ga adatoms on the GaAs(001)-(2 x 4)beta 2 surface, since the formation of Ga dimers reduces the number of electrons remaining in Ga dangling bonds. Lattice sites in the missing dimer row near a kink and B-type step edge are stable for a Ga adatom, whereas no preferential adsorption site is found near an A-type step edge. This is simply because a Ga adatom in the missing dimer row near a kink and B-type step edge is weakly stretched by an As atom and As-dimer on the plane one layer below as opposed to being strongly stretched by two As-dimers near an A-type step edge.