Extremely low current measurements of semiconductor heterostructures and nanostructures at cryogenic temperatures

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Crystalline semiconductors are the foundation of telecommunications, computing, and many other technologies employed in all aspects of contemporary life. Their physical characteristics are determined both by the properties of the host crystal and by the presence of impurities and crystalline defects. The identification and control of these defects determines the commercial viability of a given new material or structure. Combined with control of growth and processing factors, the influence of crystalline defects and impurities at surfaces, interfaces and in the bulk semiconductor can be distinguished and enhanced or eliminated. A new capability to make extremely sensitive electrical measurements at temperatures below 80K is needed to extend the energy range of carrier trapping experiments and also to investigate the effects of surfaces and interfaces on transport properties in novel nanostructures, including nanowires. We request funding to acquire a closed-cycle He cryostat for electrical measurements of a variety of semiconductors and nanostructures in the temperature range 4-300K. In addition, we propose to purchase an electrical measurement system capable of detecting electrical currents as low as 10 to the power -15 Amperes (1fA), required for studies of their electronic properties.