The role of oxygen in optical activation of Er implanted in Si

The results of high resolution photoluminescence studies of erbium-implanted Czochralski-grown (CZ) and float-zone (FZ) silicon are presented. We show that the photoluminescence (PL) spectrum of cubic Er centers observed in CZ Si annealed at 900 °C is the dominant emission in FZ Si for the same annealing conditions. We assign it to an isolated interstitial erbium site and not to an octahedrally coordinated ErO complex. We resolve the PL lines of two ErO related centers with lower site symmetry (not found in FZ Si). The internal PL efficiency of the ErO defects is probably higher than that of isolated centers; however, the overall PL yield is rather controlled by the rate of energy transfer from excitons recombining at Er sites.