Si1-xGex growth instabilities on vicinal Si(001) substrates: Kinetic vs. strain-induced effects - art. no. 041301

A comparative study of kinetically and thermodynamically driven instabiliti es on vicinal Si(001) surfaces during overgrowth with Si1-xGex is reported. We mapped out a wide range of the multidimensional growth parameter space and found. in contrast to previous reports, no evidence for strain-induced step bunching. At low Ge concentrations strain is insufficient to promote s train-induced step bunching, and the modified surface kinetics in the prese nce of segregated Ge leads to a smoother rather than rougher morphology. Hi gh Ge concentrations around 50% could be expected to provide enough strain, but near equilibrium hut cluster formation is the more effective strain-re laxation mechanism. We found the characteristically rippled step-bunching m orphology only in a kinetically limited growth regime. where strain is of l imited relevance, and in experiments where the SiGe layers replicate an und erlying ripple morphology.