Donor activity of ion-implanted erbium in silicon

Hall measurements performed in the temperature range 4-300 K on Er+ implanted silicon revealed the existence of shallow and deep donor states. Samples implanted with Er+ alone show a shallow level at 8-14 meV below the conduction band edge and a deep level at 60-100 meV. Coimplantation with O+ or S+ shifts the levels deeper into the gap or introduces additional donor levels. The concentration of the shallow level depends on implantation and annealing parameters and amounts up to 10% of the implanted Er. It is suggested that the donor levels play an important role for the excitation and deexcitation processes of the Er luminescence in Si.