Doping in Non-Planar Heterostructures

技术描述：与传统的平面异质结构相比，非平面异质结构，特别是核壳纳米线，在光电应用中表现出许多相对优势。然而，对掺杂物分布和界面形态的分析是极具挑战性的，这限制了对优化结构和性能所需的基本生长过程的理解。本项目研究了在由Si-Ge和GaAs-AlGaAs核壳纳米线组成的非平面异质结构中控制掺杂和合金元素掺入、扩散和偏析的驱动力。为此，原子探针层析成像、霍尔效应测量、开尔文探针力显微镜和微光致发光被用于将掺杂水平和成分波动与电子和光学性质联系起来。在加工过程中的掺杂扩散和器件结构中的电输运的数值模拟是基于原子探针研究提供的定量的、原子尺度的成分信息，并与之进行比较。非技术描述：新材料和新形式的传统材料可以改进现有技术并导致新技术的创造。这个项目正在发展对已知半导体材料（如硅和砷化镓）如何以新的方式组合在一起以更好地执行重要功能的基本理解，例如光能和电能的有效转换。研究活动重点是非平面异质结构，其中“异质结构”是指两种不同材料的结合，“非平面”是指这些材料之间的连接处具有复杂的三维形式，以便更好地实现关键器件功能。为了分析非平面异质结构的形状和其中微量控制电荷的掺杂原子的分布，使用了一种称为原子探针层析成像的高度专业化的显微镜。原子探针可以观察迄今为止制造的最小设备的内部，并绘制出存在的所有元素的分布。该项目结合了新技术材料开发的工业视角，包括一个“校园合作”项目，在这个项目中，与研究的更大目标相关的本科生研究项目从工业合作伙伴那里征求。

Technical Description: Non-planar heterostructures, particularly core-shell nanowires, exhibit a number of comparative advantages for optoelectronic applications with respect to conventional planar heterostructures. The analysis of dopant distribution and interface morphology is extremely challenging, however, limiting the understanding of fundamental growth processes that is needed to optimize the structure and properties. This project investigates the driving forces that control dopant and alloy element incorporation, diffusion, and segregation in non-planar heterostructures consisting of both Si-Ge and GaAs-AlGaAs core-shell nanowires. To this end, atom probe tomography, Hall effect measurements, Kelvin probe force microscopy, and micro-photoluminescence are used to relate doping levels, and fluctuations in composition, to electronic and optical properties. Numerical modeling of dopant diffusion during processing and electrical transport in device structures is based on and compared with quantitative, atomic scale composition information provided by the atom probe studies.Non-technical Description: New materials, and conventional materials in new forms, can improve existing technologies and lead to the creation of new technologies. This project is developing a fundamental understanding of how known semiconductor materials, such as silicon and gallium arsenide, can be put together in new ways to better perform important functions, such as the efficient conversion of light to electrical energy and vice versa. The research activity is specifically focused on non-planar heterostructures, where "heterostructure" indicates the combination of two distinct materials and "non-planar" indicates that the junction between these materials has a complex three-dimensional form so as to better carry out key device functions. To analyze the shape of non-planar heterostructures and the distribution of tiny quantities of charge-controlling dopant atoms within them, a highly specialized microscope known as an atom probe tomographic is employed. The atom probe can look inside the very smallest devices that have ever been made and map out the distribution of all the elements that are present. The project incorporates an industrial perspective on the development of materials for new technologies by including a "co-op on campus" program, in which undergraduate research projects of relevance to the larger goals of the research are solicited from industrial partners.