Atomic-scale properties of the amphoteric dopant Si in GaAs(110) surfaces

The electronic properties of positively charged Si-Ga donors and negatively charged Si-As accepters in different subsurface layers as well as Si donor-Si acceptor dipoles and uncharged Si pairs in GaAs(110) surfaces were investigated by scanning tunneling microscopy. The subsurface location of the dopant atoms is determined from the observed symmetry. Localized states of the dopant atoms are identified. The fraction of Si atoms incorporated in GaAs on As sites increases with increasing Si concentration. Si pairs are found to be incorporated substitutionally in GaAs and their contrast indicates the presence of half-filled dangling bonds. The Si-Ga donor-Si-As acceptor dipoles are surrounded by a height change indicating a dipole screening field. (C) 1998 Elsevier Science B.V. All rights reserved.