Effects of oxygen coimplantation on the formation of donor centers in erbium-implanted silicon

Three kinds of dominating donor centers formed in erbium-implanted silicon due to postimplantation annealing in the range from T=700 to 900°C are studied. Shallow donors with ionization energies between 20 and 40 meV are attributed to electrically active oxygen aggregates with the involvement of intrinsic defects. Two other kinds of donors at ≈EC–70 and –120 meV are identified as [Er-O] complexes. The latter donors undergo modifications at T=800°C. As a result, donor centers at ≈EC–150 meV are formed. New donors at ≈EC–100 meV also make their appearance after annealing to T=900°C.