Analysis of microstructures in SiGe buffer layers on silicon-on-insulator substrates

Microstructures in strain-relaxed SiGe buffer layers grown on silicon-on-insulator (SOI) substrates have been analyzed. The growth of strain-relaxed SiGe layers was achieved by two methods, a Ge-condensation method and a strain-relaxation method using a pure-edge dislocation network. We measured the surface morphology, dislocation structure, and crystalline mosaicity of the strain-relaxed SiGe layers and investigated the influence of various growth parameters. Transmission electron microscopy revealed residual strain-undulation elongating approximately along two orthogonal in-plane (110) directions in a strain-relaxed SiGe layer formed by the Ge-condensation method. On the other hand, the morphology of pure-edge dislocations buried at the SiGe/SOI interface was dependent on the sample structure as well as the annealing process, both of which critically determine dislocation propagation in the SiGe layer. A clear correlation was obtained between the dislocation morphology in the SiGe layer and the crystalline mosaicity measured by X-ray diffraction analysis.