It was found that, in metalorganic chemical vapor deposited Er-doped and O-doped samples at ambient pressure, only the ErGa-2O center was excited by above-bandgap host photo-excitation. It exhibited a sharp infra-red luminescence spectrum which was due to intra-4f transitions of the Er3+ ion. At high pressures, at least 2 other Er centers became optically active via host excitation. One of these pressure-induced centers was attributed to a certain Er center, which had a slightly different atomic configuration to that of the ErGa-2O center, after comparing pressure-induced photoluminescence spectra to site-selective photoluminescence spectra.

K.Takarabe, T.Mizushima, S.Minomura, R.A.Hogg, A.Taguchi, K.Takahei: Applied Physics Letters, 1997, 71[1], 93-5