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

晶体半导体是电信、计算机和许多其他技术的基础，这些技术应用于当代生活的各个方面。它们的物理特性既由基体晶体的性质决定，也由杂质和晶体缺陷的存在决定。这些缺陷的识别和控制决定了给定新材料或结构的商业可行性。结合对生长和加工因素的控制，可以区分并增强或消除表面、界面和块状半导体中晶体缺陷和杂质的影响。为了扩展载流子捕获实验的能量范围，以及研究表面和界面对新型纳米结构（包括纳米线）输运特性的影响，需要在低于80K的温度下进行极其敏感的电测量的新能力。我们申请资金购买一个封闭循环He低温恒温器，用于在4-300K温度范围内对各种半导体和纳米结构进行电测量。此外，我们建议购买一个电气测量系统，能够检测低至10的-15次方安培（1fA）的电流，以研究其电子特性。

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.