The behavior of luminescence spectra and structural defects in single crystal Czochralski silicon after erbium implantation at 1 MeV energy and 1×1013 cm-2 dose with subsequent annealing at 1100 °C for 0.25–3 h in an argon or chlorine-containing ambience was studied by photoluminescence (PL), transmission electron microscopy, and chemical etching/Nomarski microscopy. We have found that annealing in the chlorine-containing ambience gives rise to dislocation loops and pure edge dislocations with dominant dislocation-related lines in the PL spectrum. Pure edge dislocations are responsible for the appearance of the lines. The Er-related lines due to the intra-4f shell transitions in the rare-earth ions dominate in the PL spectra and no structural defects are observed after annealing in argon. The observed differences in the optical and structural properties of Si:Er are associated with intrinsic point defects generated during the implantation and annealing. © 1998 American Institute of Physics.