Comparative study of photoluminescence of undoped and erbium-doped size-controlled nanocrystalline Si/SiO2 multilayered structures

Spectra and transients of the photoluminescence (PL) of undoped and Er-doped size-controlled nanocrystalline Si/SiO2 multilayered structures with mean nanocrystal size of 1.5-4.5 nm have been comparatively investigated. The Er-doped structures exhibit a strong Er-related PL band at 0.81 eV, while the efficiency of the intrinsic PL band of Si nanocrystals at 1.2-1.7 eV decreases by several orders of magnitude in comparison with the undoped structures. At low temperature the PL spectra of the Er-doped structures show several dips separated by the energy of Si TO-phonon and bound to the transition energies between the second and third excited states to the ground state of Er3+. The Er-related PL is characterized by lifetimes of around 3-5 ms, a weak temperature quenching, and a high efficiency, which is comparable or even stronger than that of the intrinsic PL in the corresponding undoped samples. This efficient sensitizing of the Er-related luminescence is explained by the structural properties of the samples, which favor a strong coupling between the excitons confined in Si nanocrystals and upper excited states of the Er3+ ions in the SiO2 matrix. (C) 2004 American Institute of Physics.