First-principles study of Si incorporation processes on a GaAs(111)A surface

Si incorporation processes on a GaAs(1 1 1)A surface were investigated by u sing the first-principles pseudopotential method. We found that the most st able adsorption site for a single Si atom is a Ga lattice site of the GaAs lattice, but that the Si atom is pushed out from the site when Ga-As-Si mic rostructures are formed on the surface. We also found that a Si atom remain s at the Ga lattice sire when it couples with three As adatoms. These findi ngs qualitatively explain the experimentally observed properties of Si-dope d GaAs layers, i.e., that the layers are p-type under conventional growth c onditions and they become n-type under very high As pressure. (C) 2001 Else vier Science B.V. All rights reserved.