A spectroscopic study was made of samples of Er- and O-doped material which had been grown by means of metalorganic chemical vapor. It was found that photoluminescence under host excitation was dominated by a luminescence that was due to the existence of the Er-2O center (an Er atom at a Ga site, coupled to 2 adjacent O atoms). The presence of differing Er centers was demonstrated by the detection of 4I15/2  4I11/2 intra-4f shell transitions, using photoluminescence excitation spectroscopy. Transitions between these crystal-field split 4f shell levels were observed at about 1.26eV (980nm). Two lines were attributed to the Er-2O center. This permitted semi-quantitative measurements to be made of the relative concentrations of various centers. Photoluminescence spectroscopy was used to study the trap levels that were related to the Er-2O center, but no evidence was found for such a trap level in this energy range.

R.A.Hogg, K.Takahei, A.Taguchi: Journal of Applied Physics, 1996, 79[11], 8682-7