An extensive study was made of the role which was played by point defects; especially the anion antisite in material which was grown at low temperatures. The use of optical spectroscopy revealed a high concentration of AsGa, in both the neutral and positive charge states, for low-temperature material which had been grown and annealed at different temperatures. Electrical measurements of the resistivity and transient current gave consistent results, with an activation energy of 0.8eV. All of the experiments showed that the Fermi energy was pinned to the mid-gap, very close to the AsGa0/+ donor level. The lattice expansion in low-temperature material was shown to be linearly related to [AsGa]. In addition, it was suggested that the AsGa were compensated by Ga vacancies.

A.Prasad, X.Liu, H.Fujioka, N.D.Jaeger, J.Nishio, E.R.Weber: Materials Science Forum, 1995, 196-201, 189-94