Photoluminescence and photoluminescence excitation spectroscopic studies were carried out at 6K on the 1540nm 4I13/2  4I15/2 emission of Er3+ in Er-implanted films which had been grown by metalorganic chemical vapor deposition. The photoluminescence excitation spectra exhibited several broad below-gap absorption bands which excited 3 distinct site-selective Er3+ photoluminescence spectra. The excitation of 2 of these site-selective bands involved optical absorption by defects or background impurities, rather than direct intra-f shell absorption; with subsequent non-radiative transfer of the energy to nearby Er3+ luminescence centers. The characteristics of the photoluminescence excitation spectrum of the third site-selective photoluminescence band suggested that an exciton, bound at an Er-related trap, was involved in the excitation mechanism.

S.Kim, S.J.Rhee, D.A.Turnbull, E.E.Reuter, X.Li, J.J.Coleman, S.G.Bishop: Applied Physics Letters, 1997, 71[2], 231-3