Spectral-luminescence properties of freestanding porous SiC layers

We report about structural and photoluminescence properties of porous silicon carbide formed by electrochemical etching of SiC plate. The existence of a crystallite size gradient is shown across the layer. The spectrum of the photoluminescence is observed in the visible region and can be fitted at least by three peaks. The obtained photoluminescent properties are discussed with the results of the SEM, TEM and Raman studies. The nature of the low-energy peak is explained by electron-hole recombination at some localized states; the middle energy peak is related to the surface defect centers introduced by the HF reaction on the Si surface (CFO), the high energy peak can be explained by SiC nanocrystallites.