Growth of highly luminescent silicon nanocrystals by rapid thermal chemical vapor deposition

We investigate the growth of highly luminescent silicon nanocrystals by rapid thermal chemical vapor deposition (RTCVD), employing SiH4 and N2O as source gases. For [N2O]/[SiH4] = 7 similar to 8 and a growth temperature of 650degreesC, we obtain the optimized deposition condition for silicon rich oxide (SRO) layer having highly luminescent Si nanocrystals after post-deposition annealing. The cross sectional transmission electron microscope investigation reveals the existence of Si nanocrystals in the SRO matrix. Thus, the photoluminescence (PL) from the SRO layer is attributed to the quantum confinement effect of carriers in Si nanocrystals. Based on a single layer growth study, we fabricate ultra-thin SRO/SiO2 superlattice having 25 periods on a 3-inch Si wafer. The superlattice has continuous thickness variation from the center to the edge positions of the Si wafer due to inherent wafer temperature variation during growth. Photoluminescence spectra show a systematic blue-shift from a thicker position (center position) to a thinner position (edge position) which is indicative of nanocrystal size control by SRO layer thickness in the superlattice.