Synthesis of silicon quantum dot buried SiOx films with controlled luminescent properties for solid-state lighting

Highly luminescent Si quantum dot embedded SiOx films were studied as down-converting emitters for solid-state lighting applications. Strong red photoluminescence was observed from these Si nanocrystal embedded films prepared by thermal evaporation of SiO in vacuum or an O2 atmosphere followed by anneal at 1100 ◦C. The stoichiometry (1.0 < x < 1.9) and refractive indices (1.5–1.75) of these films could be well controlled by varying the oxygen flow rate and the deposition rate. The emission peak shifted from 840 to 745 nm with increasing O2 flow rate due to a decrease in the size of the Si QDs. Two excitation bands, peaked at 280 and 370 nm, were observed from these samples. The 370 nm band was much stronger than the 280 nm band, which is near the UV LED emission range required for solid-state lighting applications. Blue and green emissions were also observed from samples annealed at a lower temperature.