Defect and dislocation structures in low-temperature-grown Ge and Ge_1−xSn_x epitaxial layers on Si(110) substrates

We have investigated the epitaxial growth and crystalline properties of Ge_1−xSn_x layers on a Si(110) substrate. We found that the twin growth in the Ge epitaxial layer deposited on the Si(110) using molecular beam epitaxy at a low temperature of 200 °C can be effectively suppressed by the incorporation of 2.0% Sn. We also examined the strain relaxation of annealed Ge_1−xSn_x/Si(110) samples. The degree of strain relaxation is enhanced by the annealing process, and the threading dislocation in the Ge_1−xSn_x layers decreases from 10¹¹ cm⁻² to 10¹⁰ cm⁻² because of the propagation of misfit dislocations. We also observed misfit dislocations formed at the Ge_1−xSn_x/Si interface, which would effectively promote isotropic strain relaxation in the Ge_1−xSn_x layers. - Highlights: • Suppression of twin in GeSn growth on Si(110) substrate • Isotropic strain relaxation of Ge and GeSn layers by misfit dislocation network • Achievement of high quality GeSn epitaxial layers on Si(110) by post deposition annealing