High-resolution channeling contrast microscopy of compositionally graded Si_1-XGe_X layers

Epitaxial Si_1-xGe_x layers have a wide range of applications in microelectronic and optoelectronic devices. One of the possible SiGe configurations involves the growth of Si_1-xGe_x on a virtual substrate (VS). The VS is grown by linearly grading the Ge composition of the Si_1-xGe_x layer up to the final desired Ge composition for subsequent device growth. Such VSs are designed to accommodate the misfit strain between the substrate and the overlying active layer. However, a cross-hatch surface morphology often results which affects subsequent device layer growth on the VS. In this paper, we report on high-resolution channeling contrast microscopy (CCM) on such VSs. CCM measurements give both lateral and depth-resolved information on the cross-hatch features observed. The channeling RBS maps reveal a slight lattice plane bending in adjacent bands of width of ~10 μm, consistent with the relaxation of the SiGe layer. In addition, the Ge concentration distribution was imaged by proton induced X-ray emission, in order to check if the cross-hatch is associated with increased Ge concentrations.