Red luminescence from Si quantum dots embedded in SiO x films grown with controlled stoichiometry

Abstract

Silicon quantum dot (QD) based luminescent structures can emit throughout the visible region by controlling their size and/or the host matrix. Consequently, multiple sized Si QDs embedded in thin films could be used to produce efficient white light sources, when integrated with a blue/UV LED, and film structures designed for high light extraction. In this paper, we report strong red photoluminescence from Si QDs embedded in films prepared by thermal evaporation of SiO in vacuum or an O₂ atmosphere. The SiO_x film composition (1.0< x <1.9) was controlled by varying the deposition rate and the oxygen flow rate in the chamber. After annealing at 1100°C, silicon nanocrystals of 20nm to 2nm in size were formed in films with different stroichiometry, as indicated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterization. Red photoluminescence was observed from films with Si QDs smaller than ~5nm, and attributed to confined carrier radiative recombination in the Si QDs. The emission peak shifted from 840nm to 745nm with increasing O₂ flow rate due to a decrease in the size of the Si QDs.