OPTICAL-CENTERS AND OXYGEN IN ER-ION IMPLANTED SILICON

Systematic photoluminescence (PL) studies of silicon co-implanted with erbium and oxygen are presented. We find a strong dependence of PL sp ectra on the ratio of O/Er, For samples with Er peak concentration of 1 x 10(19) cm(-3), annealed at 800 degrees C, the well-defined Er lumi nescence spectra arising from Er3+-centers with cubic site symmetry ha ve been observed to dominate the PL spectra in the O/Er ratio of one t o two. In addition, Rutherford backscattering spectrometry (RES) and c hanneling measurements revealed significant recovery of the crystal qu ality in the same O/Er ratio. In the O/Er ratio larger than 5, other l ines emerge in the PL spectrum, and the PL from cubic symmetry centers decreases in intensity. We suggest that the origins of optical center s with cubic site symmetry are Er3+ ions in tetrahedral sites coupled with O, while oxygen aggregation around Er ions becomes predominant in the O/Er ratio larger than 5.