Temperature dependence of steady and time-resolved photoluminescence in Si quantum dots/SiO2 superlattices

Superlattices of amorphous silicon rich oxide (a-SiOx) and silicon dioxide (SiO2) have been deposited by plasma enhanced chemical vapor deposition technique, and Si quantum dots (Si-QDs) are obtained in the a-SiOx layers by the following annealing treatment. Steady and time-resolved photoluminescence (PL) spectra at different temperatures are measured. Two broad PL bands located in the regions of 1.2-1.6 eV and 2.1-3.1 eV are obtained at low temperature, and they are defined as S band and F band, respectively. The PL decay time of the samples increases rapidly with decreasing temperature. Analyses show that the recombination dynamics of S band is related to the dispersive motion of excitons, and its PL lifetime is associated with an upper level singlet state and a lower level triplet state, while that of the F band is related to the recombination of oxygen related defects.