Silicon nanocrystals (Si NCs) embedded in a dielectric matrix showing tunable band gap properties have recently emerged as attracting top absorbers in silicon based high efficiency multijunction devices. This paper presents optical and electrical characterization of Si NCs in SiC matrix resulting from annealing at 1100°C of silicon-rich carbide (SRC)/SiC multilayers produced by Plasma Enhanced Chemical Vapour Deposition (PECVD), varying either the Si content in the SRC or the SiC thickness. Simulation of Reflectance and Transmittance spectra in the UV-Vis revealed that 1) the Si crystallization increases with increasing Si content; 2) a severe shrinkage of the multilayers occurs upon annealing due to the release of hydrogen and to crystallisation; 3) the growth of nanocrystals is affected by atomic environment and diffusivity of involved atoms at the investigated temperature. Temperature dependent conductivity measurements are performed on multlayers and on reference layers. The results show evidence of defect state conduction in the SiC matrix.