Local density functional cluster calculations were carried out on SiGa-As-X complexes, where X was Li, Be, Cu, Zn or a vacancy. It was found that the donor and acceptor moved away from each other; contrary to a simple argument which was based upon Coulomb attraction between them. It was concluded that this explained the insensitivity of the Si-related local vibrational modes to the identity of the impurity, and their similarity to the case where X was a vacancy.

R.Jones, S.Oberg: Semiconductor Science and Technology, 1994, 9[12], 2291-4