SELF-ORGANIZATION DURING SI1-YCY ALLOY LAYER GROWTH ON SI(001) USING HOMOGENEOUS COEVAPORATION

We show that the formation of self-organized pseudosuperlattices durin g homogeneous epitaxial growth of Si1-yCy on Si(001) is a fundamental phenomenon not limited to special growth techniques. For samples grown at higher temperatures, and therefore, with higher concentration of n onsubstitutional carbon, we find contrast variations in cross-sectiona l transmission electron microscopy, roughly periodic in the growth dir ection in epitaxial Si1-yCy alloy layers. The periodicity is a monoton ic function of growth temperature and growth rate. Although the final explanation of this phenomenon remains an open question, we are able t o rule out several possible effects. These structures do not reflect a modulation in the substitutional C content, the formation of the C-ri ch SinC phases, or the segregation of nonsubstitutional C-containing d efect complexes up to a certain saturation level. Rather, we show that the layers formed during the different growth processes contain diffe rent amounts of carbon. There is no critical size of the C-containing defect complexes independent of growth conditions that could lead to t he formation of the observed structures. The variation of the periodic ity with growth rate and temperature is similar to surface diffusion p rocesses with an activation energy of 0.94+/-0.04 eV, close to the Val ue for Si adatom diffusion on a Si(001) surface. (C) 1997 American Ins titute of Physics.