Understanding crystal growth and electronic properties of semiconductor nanowires and nanostructures

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The focus of my research program is in the rapidly emerging area of semiconductor nanowire materials and applications. Continued progress towards increased functionality and performance in semiconductor devices will require the ability to fabricate structures in which electrons are highly confined in more than one dimension. There are several key issues to be addressed before semiconductor nanowires can be incorporated into useful applications, namely: 1) how to control the growth of defect free nanowires both along the length of the wire, as well as in the radial direction, in order to form various "core-shell" structures for specific device applications; 2) how to measure the electrical conductivity in these very small structures; and 3) how to control the electrical conductivity by means of doping. We will address these questions for certain specific materials combinations, such as III-V semiconductor materials, which will be developed into prototype devices with applications in quantum computing, infrared sensing, and solar energy. Prototype p-n junction structures will be fabricated by metalorganic vapour phase epitaxy (MOVPE) and their electrical properties will be studied using a nanoprobe inside a scanning electron microscope. A significant portion of the proposal will involve extending our recent progress in this area to zinc oxide, a material with great potential for light emitting devices in the visible and ultraviolet. Despite more than a decade of intense effort on this material, many important questions remain, such as: 1) what are the physical mechanisms behind catalyst free nanowire growth; 2) what is the underlying cause of the residual n-type conductivity; and 3) what are the mechanisms responsible for the observed p-doping? We will exploit the high crystalline quality of nanowires grown by our MOVPE process, together with our expertise in semiconductor doping, optical spectroscopy, and in situ electrical measurements to address these questions. The results obtained from this research will lead to the development of device applications that will provide benefits to Canada's semiconductor industry, for example in the fields of advanced lighting technologies, telecommunications, and solar energy.