ELECTRICAL AND OPTICAL CHARACTERIZATION OF ER-IMPLANTED SI - THE ROLEOF IMPURITIES AND DEFECTS

The electrical and optical properties of Er-implanted Si are shown to be critically dependent on the presence of impurities and defects. A l arge enhancement in the electrical activation of Er (up to three order s of magnitude) is obtained by coimplanting Er with O or C at 300-degr ees-C. The use of C also allows one to obtain a good quality crystal a fter implantation and annealing. This is shown to be crucial in the ph otoluminescence process. In fact, in spite of the large amount of acti ve Er atoms, photoluminescence is inhibited in the presence of the hig h concentration of precipitates and crystallographic defects which are left after annealing of the Er and O coimplants. The photoluminescenc e intensity is, on the other hand, enhanced by the high concentration of active Er atoms in the defect-free crystal which is left after anne aling of the Er and C coimplants. Moreover, a clear shift in the main photoluminescence peaks is observed in Er- and C-coimplanted samples a s a result of the different surroundings experienced by the Er atoms.