The growth and device applications of ultra-thin epitaxial semiconductor layers will be investigated. Growth experiments will involve the application of the Limited Reaction Processing technique to minimize the thermal exposure of strained layers. The technique also allows for the in-situ growth of multiple layers of different composition. Such in-situ processing could be a crucial step in meeting the uniformity and yield requirements of future generations of VLSI technology. The use of vapor phase source gases also gives a process that has the potential to be easily scaled up for industry. The device experiments will exploit the material properties of these layers to develop new kinds of electronic and opto-electronic devices. Fundamental studies of the electronic properties of these layers, and their dependence on growth techniques, as well as actual device fabrication are planned. Initial experiments will be designed to explore the SiGe system and other silicon-based heterostructures.