Optical and structural properties of SixSnyGe1-x-y alloys

Single-phase SixSnyGe1-x-y alloys (xless than or equal to0.25,yless than or equal to0.11) 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 E-2 critical point, as expected based on the E-2 values of Si and Ge. (C) 2004 American Institute of Physics.