Surfactant-mediated Si quantum dot formation on Ge(001)
Stranski–Krastanow growth, modified by the presence of submonolayer coverages of carbon or antimony, is investigated for tensile strained silicon epilayers on Ge(001) substrates. We find a reduction in the wetting layer thickness from >10 monolayers without surfactant, to 7.5 and 4.5 monolayers, respectively, with Sb and C predeposition. Very small islands with an aspect ratio of 0.05 and a narrow size distribution were found for Sb-mediated growth. For both adatom species the wetting layer is free of dislocations, whereas the Si islands are almost completely strain relaxed, mainly via sessile 90° misfit dislocations. We show that early dislocation nucleation is an inherent property of a (001) oriented cubic heterosystem under tensile strain.