DEGREE OF CRYSTALLINITY AND ELECTRICAL TRANSPORT-PROPERTIES OF MICROCRYSTALLINE SILICON CARBON ALLOYS

The structural and electrical properties of undoped microcrystalline silicon-carbon films deposited by plasma-enhanced chemical vapour deposition are analysed. Raman spectroscopy and high-resolution transmission electron microscopy suggest that the films are constituted of silicon microcrystals, surrounded by a grain-boundary region, or interconnected or separated by a hydrogenated amorphous silicon carbide channel. The dependences of the electrical transport properties upon the structure of the films are examined and interpreted in terms of different conductivity mechanisms. The dark conductivities as a function of temperature in the range 300-420 K show a dependence on the degree of crystallinity of the films. The proposed models seem to fit the experimental results well.