Size dependent photoluminescence of SiC nanocrystals

The paper presents the results of porous SiC study using photoluminescence and scanning electronic microscopy. It is shown that the intensity of defect-related PL bands (2.08, 2.27, 2.44 and 2.63 eV) increases monotonically with the rise of PSiC thickness from 2.1 up to 12.0 μm. These luminescence centers are assigned to surface defects which appear at the PSiC etching process. Photoluminescence intensity stimulation for surface defects is attributed to rise of defect concentrations with increasing of porous layer thickness and to realization of the hot carrier ballistic mechanism at surface defect excitation. Intensity enhancement for exciton-related PL bands (2.79, 2.98 and 3.26 eV ) is attributed to increasing the exciton recombination rate as result of exciton weak confinement in big size SiC NCs of different polytypes (6H-PSiC with inclusions of 15R- and 4H-PSiC).