The diffusion and clustering of supersaturated substitutional C in 200nm-thick SiGeC layers buried under a Si cap layer of 40nm were investigated. The samples were annealed in either inert (N2) or oxidizing (O2) ambients at 850C for times ranging from 2 to 10h. The Si self-interstitial (I) flux coming from the surface under oxidation enhanced the C diffusion with respect to the N2 annealed samples. In the early stages of the oxidation process, the loss of C from the SiGeC layer by diffusion across the layer/cap interface dominates. This phenomenon saturates after an initial period of 2 to 4h which depended upon the C concentration. This saturation was due to the formation and growth of C containing precipitates which were promoted by the I injection and act as a sink for mobile C atoms. The competition between clustering and diffusion was considered for 2 different C concentrations.

Diffusion and Clustering of Supersaturated Carbon in SiGeC Layers under Oxidation. E.Napolitani, D.De Salvador, A.Coati, M.Berti, A.V.Drigo, M.S.Carroll, J.C.Sturm, J.Stangl, G.Bauer, C.Spinella: Nuclear Instruments and Methods in Physics Research B, 2002, 186[1-4], 212-7