Low-dislocation-density strain relaxation of SiGe on a SiGe/SiGeC buffer layer

摘要

We report an observation of strain relaxation in lattice-mismatched heteroepitaxial Si_(1-x)Ge_x layers, accompanied by a reduction in threading dislocation density (TDD). This occurs on a Si_(0.77)Ge_(0.23) layer grown on top of alternating layers of Si_(0.77)Ge_(0.23)/Si_(0.76)Ge_(0.23)C_(0.01). The present scheme allows us to grow a high-quality 85% relaxed Si_(0.77)Ge_(0.23) layer with a TDD of ～10~4/cm~2. The high-resolution transmission electron microscope results showed the presence of Si_(1-x-y)Ge_xC_y, domains (with x≤0.23 and y≤0.01) after annealing at 1000℃. We infer that the formation of these domains assist the low TDD relaxation by releasing the epitaxial misfit strain as localized discrete strain and by blocking the propagation of misfit dislocations.