Improvement of the Visible Electroluminescence from Nanocrystalline Silicon Embedded in CaF₂ on Si(111) Substrate Prepared by Rapid Thermal Annealing

Electroluminescence (EL) from nanocrystalline Si (nc-Si) embedded in a single-crystal CaF₂ layer formed on a p-type Si(111) substrate has been demonstrated. Nc-Si/CaF₂ layers were grown by co-evaporation of Si and CaF₂ by molecular beam epitaxy for Si and partially ionized epitaxy for CaF₂ at a low growth temperature, followed by rapid thermal annealing (RTA) in N₂ ambient. The crystal growth and annealing conditions were optimized by investigation of the surface morphology and photoluminescence (PL) intensity. Visible EL was observed at room temperature in the dark with the naked eye, from the entire surface of the transparent electrode for current injection. The uniformity and intensity of the luminescence was drastically improved by RTA in N₂ ambient.