Time response of 1.54 μm emission from highly Er-doped nanocrystalline Si thin films prepared by laser ablation

Er-doped nanocrystalline Si thin films have been controllably prepared over the Er density of 1019–1021 cm−3 using a prescribed amount of Er in a bulk target by laser ablation. Intense photoluminescence at 1.54 μm originating from intra-4f shell transitions in Er3+ ions has been observed. The increase of Er density cannot immediately result in a linear increase in Er3+-emission intensity. The time response measurement indicated that the change in the rise time of the Er3+ emission directly shows that Er3+ ions are excited by the energy transfer associated with the recombination of electron–hole pairs generated optically in the Si host. We found that the decrease of the excitation efficiency of Er3+ ions was responsible for the suppression of the Er3+-emission intensity in highly Er-doped nanocrystalline Si thin films.