The formation of donor centres was studied in Czochralski-grown samples which had been doped (Dy, Ho, Er, Yb) by means of ion implantation. Three kinds of donor, with ionization energies of less than 0.2eV, were formed upon annealing at 700 or 900C. Shallow centres at Ec – 0.04eV were attributed to O-related donors. Two types of deeper donor were associated with rare-earth ions.

Rare Earth Impurities and Impurity-Related Centers in Silicon V.V.Emtsev, V.V.Emtsev, D.S.Poloskin, E.I.Shek, N.A.Sobolev, J.Michel, L.C.Kimerling: Solid State Phenomena, 1999, 69-70, 365-70