Spectroscopic probing of defect-related energy storage in silicon doped with erbium

An enhancement of 1.5 mu m Si : Er photoluminescence by a mid-infrared puls e from a free-electron laser is investigated in detail. It is concluded tha t the effect is a consequence of defect-related energy storage in Si : Er s amples. Carriers generated by a band-to-band excitation are participating n ot only in the excitation of Er luminescence via the excitonic mechanism, b ut are also trapped at various defect states. The infrared pulse photoioniz es them, thus promoting extra carriers into the excitation channel of the E r3+ ion and leading to an additional luminescence. By scanning the waveleng th of the free-electron laser ionization spectra of shallow centers partici pating in the energy transfer are obtained. The results also elucidate a sp ecial role of oxygen in Si : Er luminescence. (C) 1999 Elsevier Science B.V . All rights reserved.