High-resolution channeling contrast microscopy of compositionally graded Si 1− XGe X layers

Abstract

Epitaxial Si 1− x Ge 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− x Ge x on a virtual substrate (VS). The VS is grown by linearly grading the Ge composition of the Si 1− x Ge 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.