9503210 Atwater This research aims at a definitive assessment of the synthesis, structure and electronic structure of a class of Group IV semiconductor alloys containing tin. New approaches to alloy synthesis will be explored to overcome thermodynamic and kinetic limits to growth of homogeneous, single-crystal, Sn-based group IV semiconductor alloys. Two types of epitaxial heterostructures are of interest: Binary alloys with large misfit relative to silicon grown either in thick strain-relieved layers or thin, coherently strained layers; and alloys where atomic size differences enable local strain compensation and low misfit relative to silicon. First principles electronic structure calculations in the local density approximation will be performed to enable determination of which structures are stable and to obtain energy band structures of strained and unstrained Sn-based alloys. Information from the electronic structure calculations will be used to construct force fields for molecular dynamics simulations of Sn incorporation using energetic beams. Measurements of electronic and optical properties (e.g. optical energy gap, carrier mobilities and carrier concentrations) of single crystal alloy films will be compared to calculated electronic and optical properties. %%% This program will be the first comprehensive investigation of a new class of materials whose electronic properties may result in the integration of new functional heterojunction electronic and optoelectronic materials and devices on silicon substrates. Because of the pervasiveness of silicon integrated circuit technology and its enormous economic importance, the technological impact of the proposed program is potentially very large. An important feature of the program is the training of students in a fundamentally and technologically significant area of materials research. ***
