InSb Heterostructures for Spin and Quantum Electronic Experiments

本项目探索InSb异质结中的自旋特性和量子效应，旨在为依赖这些现象的应用优化此类结构。近年来，专注于半导体中电子自旋性质的实验数量大幅增加。这种努力很大程度上是由一种利用自旋极化电流的新型设备的愿景推动的。仍然存在许多挑战，包括寻找最有效的自旋注入和自旋操纵的材料和构型，以及开发一系列表征自旋性质的技术。对某些装置的弹道运输要求带来了额外的挑战。窄禁带材料是一种很有前途的解决方案，因为Rashba、Dresselhaus和Zeeman能量项引起的大的自旋效应与窄禁带相关。由于InSb的带隙在所有III-V半导体中最小，因此自旋效应有望成为最大的带隙之一。PI已经成功地生长了InSb量子阱，在高达185K的温度下，通过0.5um的弹道传输证明了这一点。该方法有四个组成部分：1)将使用电子自旋共振技术来探测能量分裂。通过改变量子阱结构参数，可以确定影响拉什巴效应的因素。预计这将有助于更全面地了解拉什巴和德雷塞尔豪斯分裂，目标是优化大零场分裂的结构。2)大的Rashba和Dresselhaus机制预计会在电子聚焦实验中产生有趣的结果。具有不同自旋投射的电子的不同轨迹将通过基于磁聚焦的自旋过滤器来研究。3)研究用于研究自旋分裂的点接触技术。在这些一维通道中，自旋轨道效应被预测会导致更丰富的电导谱。由于InSb具有较大的Rashba项和较小的有效质量，从而导致较大的禁闭能，因此InSb非常适合于这项研究。4)对自旋相反的朗道能级之间和双层系统中的反交叉的磁光实验将对自旋相互作用和新的电子态提供更深入的了解。InSb基异质结构材料科学的进步使这些研究成为可能。对异质结构设计的改进建议将以晶体缺陷的透射电子显微镜研究为指导，晶体缺陷是限制电子迁移率和平均自由程的重要因素。缺陷密度将通过改进在GaAs衬底上使用的缓冲层和通过使用InSb衬底来降低。有了拟议的改进，弹道运输将持续更长的距离和更高的温度。非技术解释该项目涉及与电子和光子学有很强技术相关性的基础材料研究，并有效地将研究和教育结合在一起。这项研究超越了开发利用自旋特性的技术的相关性。研究将与各级教育相结合。外联工作包括开发和实施供K-5级学生使用的磁学单元。工程和物理专业的课程将通过在两门课程中引入自旋电子学作为一个专题来改进。最后，这项研究工作将争取到众多本科生和研究生的参与。代表人数不足的群体的成员，特别是妇女，将继续是这项研究的组成部分。

TECHNICAL EXPLANATION This project explores spin properties and quantum effects in InSb heterostructures, and aims to optimize such structures for applications that rely on these phenomena. The number of experiments that focus on spin properties of electrons in semiconductors has increased substantially in recent years. Much of this effort is motivated by a vision of new types of devices that exploit spin-polarized currents. Many challenges remain, including finding the most efficient materials and configurations for spin injection and spin manipulation, and developing a range of techniques for characterizing spin properties. The requirement of ballistic transport for some devices provides an additional challenge. Narrow band gap materials are a promising solution since large spin effects caused by the Rashba, Dresselhaus, and Zeeman energy terms are correlated with narrow gaps. Because InSb has the smallest band gap of any III-V semiconductor, spin effects are expected to be among the largest. The PIs have demonstrated success in the growth of InSb quantum wells, as evidenced by ballistic transport over distances of 0.5um at temperatures as high as 185K. The approach has four components: 1)Energy splittings will be probed using an electron spin resonance technique. By varying quantum well structural parameters, factors that influence the Rashba effect will be identified. This is expected to contribute to a more complete understanding of the Rashba and Dresselhaus splittings with the goal of optimizing structures for large zero-field splitting. 2)The large Rashba and Dresselhaus mechanisms are predicted to have interesting consequences in electron focusing experiments. The separate trajectories for electrons with different spin projections will be studied via spin filters based on magnetic focusing. 3)Point-contact techniques for studying spin splitting will be studied. In these one-dimensional channels spin-orbit effects are predicted to lead to much richer conductance spectra. InSb is well suited to this study due to both the large Rashba term and the small effective mass that leads to large confinement energies. 4)Magneto-optical experiments on anti-crossings between Landau levels with opposite spin and on bilayer systems will provide further insight into spin interactions and novel electronic states. These studies are made possible by advances in the materials science of InSb-based heterostructures. Proposed improvements to the heterostructure design will be guided by transmission electron microscopy studies of crystalline defects, which are an important factor limiting the electron mobility and mean free path. Defect densities will be reduced through modification of the buffer layers used on GaAs substrates and through the use of InSb substrates. With the proposed improvements, ballistic transport will persist to longer lengths and higher temperatures. NON-TECHNICAL EXPLANATIONThe project addresses fundamental materials research with strong technological relevance to electronics and photonics, and effectively integrates research and education. The research goes beyond its relevance to developing technologies that exploit spin properties. Research will be integrated with education at various levels. Outreach efforts include the development and implementation of a module on magnetism for use with K-5 students. The curriculum for engineering and physics majors will be improved by the introduction of spintronics as a special topic in two courses. Finally, this research effort will enlist the participation of numerous undergraduates and graduate students. Members of underrepresented groups, particularly women, will continue to be integral to the research.