Kinetic vs. strain-induced growth instabilities on vicinal Si(001) substrates

The vicinal Si(001) surfaces are known to exhibit both kinetically and ther modynamically driven instabilities during overgrowth with Si or Sice. Here, we present a comparative study that allows the discrimination of kinetic e ffects and strain-induced equilibrium effects. Under kinetic growth conditi ons, layers with low Ge content become smoother than their homoepitaxial Si counterparts. In contrast, for layers with high Ge content, hut cluster fo rmation is identified as the dominant mechanism of the epilayer to relax st rain. We find no evidence for one-dimensional strain-induced step bunching on small angle miscut substrates. Our results strongly suggest that kinetic or kinetically limited processes rather than thermodynamic effects determi ne the morphology of Si/SiGe interfaces at 550 degreesC. (C) 2000 Elsevier Science B.V. All rights reserved.