Excitation mechanism of erbium photoluminescence in bulk silicon and silicon nanostructures

We present a short review of the theoretical and experimental results concerning the problem of excitation mechanism of erbium photoluminescence in silicon and silicon nanostructures. The excitation process consists of two stages, the first being absorption of radiation by bulk silicon matrix or nanocrystals while the second is the Auger excitation of erbium ions by recombining electron–hole pairs. The large values of Auger excitation cross-section under optical pumping in semiconductor matrices are due to large values of band-to-band absorption coefficient of bulk silicon or silicon nanocrystals exceeding by several orders of magnitude the absorption coefficient of erbium in dielectric SiO2 matrix. The specific features of Auger process in silicon nanocrystals when excitation of erbium ions is produced by quantum-confined electron–hole pairs are discussed.