Photo-enhanced chemical vapour deposition of hydrogenated amorphous silicon carbon using an internal discharge lamp

Hydrogenated amorphous silicon carbon (a-Si1−xCx:H) is becoming an increasingly important technological materials with a wide and controllable bandgap. Using an internal hydrogen lamp, a-Si1−xCx:H was produced from a mixture of monosilane and methane or acetylene. Raman and TEM measurements showed that these films are highly amorphous with occasional small microcrystals. When using acetylene as the gaseous source of carbon, the refractive index decreases from 3.8 to 2.2 and the bandgap increases from 1.7 to 2.4 eV as the gas ratio (C2H2SiH4 increases from 0.25 to 2.7. When using methane, a CH4SiH4 gas ratio of the order of 10 is necessary to produce a film with a refractive index of 3.0 and the increase in the optical bandgap is limited to 0.3 eV. The photoluminescence peak energy corresponds well to the optical bandgap and the difference between the peak energy and the bandgap remains within 0.3 eV at most. The reaction mechanism of the deposition is discussed.