Misfit Accommodation, Ordering, and Stability in Semiconductor Thin Films

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9321957 Salamanca-Riba The proposed research addresses fundamental materials science issues surrounding the mechanism of lattice mismatch accommodation in semiconductor films, and the effect of lattice mismatch on the formation of ordered phases and the stability of semiconductor heterostructures. Transmission electron microscopy will be used to investigate the mechanism for misfit accommodation, structural ordering, and stability of semiconductor alloys of different systems and compositions grown on different substrates (buffer layers) to study the effect of lattice mismatch on the structure of semiconductor films. The misfit accommodation mechanism will be studied in systems with large and small lattice mismatches. Materials will be grown using either molecular beam epitaxy or metal organic chemical vapor deposition. The effects of growth parameters and growth methods on the structure and quality of the films will be investigated to obtain films with low defect density and single phase; special emphasis will be placed on understanding the critical initial stages of growth. %%% Most advanced electronic and photonic devices consist of compound semiconductor heterostructures whose structural integrity and quality are of critical importance, and very often determine the performance and applicability of a device technology. In this context, the accommodation of lattice mismatches between the different layers in a heterostructure and between the film and the substrate, is of fundamental significance. The proposed research will significantly benefit our basic understanding, control, and general ability to achieve improved materials for devices and circuits needed in the general areas of telecommunications, information processing; and high speed computing. ***