Direct spectral probing of energy storage in Si : Er by a free-electron laser

Results of a two-color spectroscopy in the visible and the mid-infrared on erbium-doped silicon (Si:Er) are presented. In the experiments, pulsed beam provided by a free-electron laser is directed on a sample under primary ab ove-band-gap excitation with another laser. It is shown that the powerful i nfrared beam can be ionize carriers localized at shallow traps. Liberation of these carriers makes them available for excitation of erbium and thereby enhances the luminescence intensity. Identification of shallow levels resp onsible for the effect is discussed. (C) 1999 American Institute of Physics . [S0003-6951(99)00352-6].