STRAIN RELAXATION IN TENSILE-STRAINED SI1-YCY LAYERS ON SI(001)

We investigated in detail the strain relaxation behaviour of metastabl e tensile-strained Si1-yCy epilayers on Si(001) by comparing the layer s before and after an annealing step using a variety of different diag nostic methods. The dominant strain-relieving mechanism is the formati on of carbon-containing interstitial complexes and/or silicon carbide nanoparticles, similar to the behaviour of carbon in silicon under the rmodynamical equilibrium conditions (concentrations below the solid bu lk solubility limit). We did not observe any carbon out-diffusion. To grow material suitable for device applications, all carbon atoms shoul d be incorporated substitutionally. There is only a very narrow temper ature window for perfect epitaxial growth of such layers, limited on o ne side by the possible formation of interstitial carbon complexes and on the other side by the deterioration of epitaxial growth at low tem peratures. The carbon concentration should not exceed a few per cent t o avoid strain-driven precipitation.