Step-bunching and strain-effects in Si1−xGex layers and Superlattices grown on vicinal Si(001)

A comparative study of kinetically and thermodynamically driven growth instabilities in the Si/SiGe heterosystem on vicinal Si(001) is reported. Single Si1−xGex-layers and Si1−xGex/Si superlattices are investigated by mapping out a wide range of the relevant growth parameter space. In contrast to earlier reports no evidence for strain-induced step-bunching is found. Single Si1−xGex layers replicate the morphology of the underlying buffer layers and tend to form hut clusters near thermal equilibrium. In Si1−xGex/Si superlattices no significant influence of the Ge-related strain on the step-bunching morphology can be seen. On the other hand, the effect of growth temperature is very pronounced, again indicating the dominant role of kinetics in the formation of step-bunches.