By means of Hall-effect measurements, the characteristics of centers which were created by Er diffusion and implantation were determined. It was shown that Er diffusion at 1100 to 1250C led to the formation of shallow acceptor centers at about Ev + 0.045eV. The concentration of these acceptors was governed largely by the type and concentration of the intrinsic point defects which predominated during annealing at high temperatures. The data indicated that the acceptor centers could be substitutional Er atoms. An analysis of electrical data on float-zone material after Er implantation indicated the existence of donor states at Ec - 0.03eV, Ec - 0.05eV and Ec - 0.09eV. After implanting Er into Czochralski material, and co-implanting Er and O into float-zone material, 3 types of donor state appeared at energies ranging from Ec - 0.03eV to Ec - 0.04eV, and at Ec - 0.06eV and Ec - 0.09eV. Variations in the annealing temperature had a marked effect upon the concentrations of these donors. The donor states were thought to correspond to Er-related complexes whose structures were similar to those of O-related thermal donors in Czochralski material.

V.V.Emtsev, O.V.Alexandrov, D.S.Poloskin, E.I.Shek, N.A.Sobolev: Materials Science Forum, 1995, 196-201, 615-20