Room temperature luminescence from (Si/SiO2)(n) (n=1,2,3) multilayers grown in an industrial low-pressure chemical vapor deposition reactor

A simple complementary metal-oxide-semiconductor compatible process for the preparation of very thin (1-5 nm thick) poly-Si layers embedded in SiO2 is presented. The process consists of repeated cycles of poly-Si deposition, oxidation, and wet etching steps. Periodic structures with up to three Si/SiO2 layers were grown using this process. Transmission electron microscopy analyses show that the layered structure can be conserved down to a Si layer thickness of 2 nm. For thinner layers the resulting structure is more granular like. Samples with a Si-layer thickness lower than 3 nm show room temperature photoluminescence at about 1.55 eV that shifts to higher energies when the thickness is further reduced. The maximum shift obtained with respect to the c-Si band gap is 0.55 eV. Intensity of the photoluminescence as a function of temperature shows a behavior similar to the one observed for 0 and one-dimensional Si structures. On the basis of the thickness dependence, the temperature dependence and the saturation studies, this emission is attributed to recombination of electron-hole pairs in quantum confined Si.