Diffusion and clustering of supersaturated carbon in sigec layers under oxidation

In this work we investigated the di.usion and clustering of supersaturated
substitutional carbon in 200 nm thick SiGeC layers buried under a silicon
cap layer of 40 nm. The samples were annealed in either inert (N2) or
oxidizing (O2) ambients at 850 °C for times ranging from 2 to 10 h. The
silicon self-interstitial (I) flux coming from the surface under oxidation
enhances 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 di.usion across the layer/cap interface dominates. This phenomenon
saturates after an initial period (2–4 h) which depends on the C
concentration. This saturation is due to the formation and growth
of C containing precipitates which are promoted by the I injection and act
as a sink for mobile C atoms. The competition between clustering and
diffusion is discussed for two different C concentrations.