PHOTO-ENHANCED CHEMICAL-VAPOR-DEPOSITION OF HYDROGENATED AMORPHOUS-SILICON CARBON USING AN INTERNAL DISCHARGE LAMP

Hydrogenated amorphous silicon carbon (a-Si1-xCx:H) is becoming an inc reasingly important technological material with a wide and controllabl e bandgap. Using an internal hydrogen lamp, a-Si1-xCx:H was produced f rom a mixture of monosilane and methane or acetylene. Raman and TEM me asurements showed that these films are highly amorphous with occasiona l small microcrystals. When using acetylene as the gaseous source of c arbon, 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 (C2H2/SiH4) increases fr om 0.25 to 2.7. When using methane, a CH4/SiH4 gas ratio of the order of 10 is necessary to produce a film with a refractive index of 3.0 an d the increase in the optical bandgap is limited to 0.3 eV. The photol uminescence peak energy corresponds well to the optical bandgap and th e difference between the peak energy and the bandgap remains within 0. 3 eV at most. The reaction mechanism of the deposition is discussed.