It was noted that an intra-4f transition, close to 1.54 in implanted Er, exhibited a rich fine structure that was due to the crystal fields of various types of defect. Groups of lines were identified which belonged to various Er-related optically active defects. These were isolated interstitial Er atoms, axially symmetrical Er complexes with O, and Er complex centers which contained residual radiation defects. It was shown that the exciton binding energies, as well as the non-radiative quenching rates, differed for different Er centers. Under optimum annealing conditions, the isolated Er interstitial exhibited the highest photoluminescence yield at temperatures above 100K.

H.Przybylinska, W.Jantsch, J.Suprun-Belevitch, M.Stepikhova, L.Palmetshofer, G.Hendorfer, A.Kozanecki, R.J.Wilson, B.J.Sealy: Physical Review B, 1996, 54[4], 2532-47