Transition from planar to island growth mode in SiGe structures fabricated on SiGe/Si(001) strain-relaxed buffers

The specifics of the two-to-three dimensional growth mode transition of pure Ge on SiGe/Si(001) strain-relaxed buffers (SRBs) were investigated. It was shown that the critical thickness for elastic relaxation is influenced not only by the lattice mismatch between the substrate and the film but also by Ge segregation and surface roughness dependent on parameters of strained layers. Critical thickness was found to be smaller for Ge grown on SiGe strain-relaxed buffers than on pure Si(001) substrates, in spite of the lesser lattice mismatch. Insertion of thin tensile-strained Si layers between Ge and SiGe strain-relaxed buffers increased the critical thickness.