The diffusion of Er at 1100 to 1250C led to the formation of shallow acceptors at Ev + 0.045eV. The acceptor concentrations depended upon the heat-treatment conditions and upon the type and concentration of intrinsic point defects. The addition of vacancies increased the acceptor concentration and the presence of interstitials decreased the concentration. These centers consisted of Er atoms in substitutional sites.

O.V.Aleksandrov, V.V.Emtsev, D.S.Poloskin, N.A.Sobolev, E.I.Shek: Fizika i Tekhnika Poluprovodnikov, 1994, 28[11], 2045-8