Hetero-epitaxial growth onto Si(100) was investigated. It was found that the epitaxial quality of these films was inferior to that of SiGe films, with a similar Si/Ge concentration ratio, when grown under identical conditions. The quality further deteriorated with increasing C content. The surface roughness, as determined using tapping-mode atomic-force microscopy, increased with increasing C or Ge content; thus suggesting that there was a transition from Frank-van der Merwe to Stranski-Krastanov growth. It was proposed that the very large mismatch between the average bond length in SiGeC (as determined by using Vegard’s law), and the equilibrium Si-C bond length, weakened the Si-C bonds and reduced the elastic range of the material; thus reducing the barrier to dislocation or stacking fault formation. A decrease in Ge incorporation, with increasing C incorporation, suggested the occurrence of a repulsive Ge-C interaction.

H.Jacobsson, J.Xiang, N.Herbots, S.Whaley, P.Ye, S.Hearne: Journal of Applied Physics, 1997, 81[7], 3081-90