Optical and structural properties of SixSnyGe1−x−y alloys

Single-phase SixSnyGe1−x−y alloys (x⩽0.25,y⩽0.11) were grown on Si using chemical vapor deposition. First principles simulations predict that these materials are thermodynamically accessible and yield lattice constants as a function of Si/Sn concentrations in good agreement with experiment. An empirical model derived from experimental SixGe1−x and SnyGe1−y binary data also provides a quantitative description of the composition dependence of the lattice parameters. Spectroscopic ellipsometry of selected samples yields dielectric functions indicating a band structure consistent with highly crystalline semiconductor materials of diamond symmetry. Incorporation of Si into SnyGe1−y leads to an additional reduction of the E2 critical point, as expected based on the E2 values of Si and Ge.