EFFECT OF COMPOSITION ON THE PROPERTIES OF AMORPHOUS-SILICON CARBIDE AT A CERTAIN OPTICAL GAP

The relationship between composition and optoelectric properties was i nvestigated for a-SiC:H alloys with a constant optical gap (E-opt) and different compositions. The compositions, hydrogen content (C-H) and carbon content (C-C), and the optical gap of a-SiC:H were successfully controlled independently. E-opt of a-SiC:H can be expressed by a line ar function of the compositions and a negative dependence of E-opt on C-C is observed for our samples. In the constant E-opt system, C-H inc reases with an increase in C-C in spite of a rise in the substrate tem perature. In particular, the increase in the Si-H-2 density is much mo re significant than that in the C-H bond density. This result suggests that the incorporated carbon atoms affect the bonding configuration b etween silicon and hydrogen. The film properties, such as photoconduct ivity and defect density, and solar cell performance become inferior b oth before and after light-soaking with an increase in C-C, namely the Si-H-2 density. The Si-H-2 bond is an important factor to consider wh en determining the stability of a-SiC:H as well as a-Si:H and a-SiGe:H .