A number of groups have demonstrated an efficient excitation transfer mechanism in erbium-doped crystalline and porous silicon. It has been postulated that this is a carrier-mediated transfer, which points to the possibility of fabricating efficient silicon-based 1.5 µm emitters.
We have previously reported the existence of a similar transfer mechanism in silicon-rich silica. In this paper we extend this study to include silicon nanopowders and demonstrate the existence of the same mechanism. Comparing the photoluminescence excitation spectra of erbium doped silica, silicon-rich silica and silicon nanopowders we show that the coupling mechanism enables broad-band pumping of the rare-earth ion.
We have also measured carrier lifetimes in the nanoclustered silicon materials using photoinduced free carrier decay. The measured lifetimes are surprisingly long (in the 2-10 millisecond regime), and we discuss the effect of this on the transfer mechanism.