Photoluminescence and microstructure of self-ordered grown SiGe/Si quantum wires

Employing self-ordered growth in convex corners of nonplanar Si substrates, SiGe quantum wires of approximately 30 nm lateral dimension were fabricated. Photoluminescence spectra of these structures are dominated by transitions originating from the quantum wires at measurement temperatures above 20 K. The energetic positions of the quantum wire transitions are in good agreement with Ge concentrations measured by spatially resolved energy dispersive x-ray spectroscopy using a scanning transmission electron microscope. We find that the Ge concentration inside the wire is considerably lower than the nominal value for growth on planar parts of the substrate. In addition we find a pronounced gradient in the Ge concentration of the wire.