Spectral photoconductivity of nanostructured silicon carbon films spectral photoconductivity of SiC thin films

Nanostructured films composed of silicon crystallites embedded in a hydrogenated amorphous silicon carbon matrix have been deposited by plasma enhanced chemical vapour deposition from silane-methane mixtures diluted in hydrogen varying the rf power. Structural, optical and photoconductivity properties of the films have been investigated. The increase in rf power in the 40-80 W range enhances the incorporation of carbon in the amorphous matrix and decreases the fraction and size of the silicon crystallites leading to an enlargement of the optical band gap from 2.07 to 2.20 eV. Steady state spectral photoconductivity measurements have been performed under monochromatic radiations in the 460-1050 nm range. It has been demonstrated that monomolecular recombination kinetics occurs in the samples under illumination and the deterioration of the phototransport properties, with increasing the rf power, are correlated to the reduction of the mobility lifetime product of the free electrons. However, the mobility lifetime product as a function of the optical band gap shows high values as in the case of device quality films deposited by silane-methane mixtures diluted in hydrogen.