Optical bandgap and quantum well model in hydrogenated amorphous silicon carbon alloy films

Abstract

Hydrogenated amorphous silicon carbon alloy (a-SiC : H) films of various composition were prepared by the rf glow discharge decomposition of acetylene and silane as well as ethylene and silane and were also annealed for various annealing temperatures. Careful and detailed IR absorption and the optical bandgap (Eopt) measurements were undertaken for a-SiC : H films of different composition (x) and annealing temperatures (Ta). Interesting variation of Eopt with x and Ta have been observed. Our study demonstrates, for the first time, that the models involving alloying or/and ordering break down and the proposed quantum well model based on heterogeneity is found to be the only model capable of explaining the observed variation of Eopt. This, consequently, may have considerable implications.