We report high resolution (<0.05 cm−1) photoluminescence (PL) spectra of erbium implanted float‐zone (FZ) and Czochralski grown (CZ) silicon. We show that the 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 isolated, interstitial erbium. We observe also two other kinds of optically active Er centers with lower than cubic site symmetry: (i) O‐related (found only in CZ Si) and (ii) those related to radiation defects. We conclude that coimplantation with light elements does not lead to the formation of Er‐codopant complexes, but rather to Er forming complexes with implantation induced lattice defects. ©1995 American Institute of Physics.