Electronic Properties of Strained Narrow-Gap Quantum Wells

本项目研究基于InSb/AlInSb异质结的2DES(二维电子系统)的材料科学和物理。与其他III-V材料相比，InSb具有极值的特征，它具有最小的禁带，最小的电子有效质量，最大的电子g因子，以及所有III-V半导体中最非抛物的导带。这些显著不同的参数使得InSb中的二维电子系统(2DES)引起了人们对替代以GaAs为基础的2DES的兴趣。尽管主体材料可以影响嵌入的2DES的物理性质，但人们对替代材料中的2DES的研究动力很小，因为大多数2DES的结晶质量都相当差。由于InSb/AlxIn1-xSb结构的迁移率与首次观察到分数量子霍尔效应的GaAs/AlxGa1-xAs结构的迁移率相当。这些高迁移率，再加上InSb 2DESs参数空间的巨大差异，为这个项目提供了动力。目的是促进InSb/AlxIn1-xSb异质外延材料科学的发展，探索InSb 2DESs的低温磁输运和磁光性质，并将采用多种方法来改善材料质量。扫描探针显微镜，连接到与分子束外延室相同的真空，将被用来评估晶格不匹配衬底上的掺杂效率和缓冲层有效性。将使用原子氢源来钝化生长表面，并促进InSb衬底上的氧化物脱附。材料质量的提高将提高低温下研究的2DESS中电子-电子相互作用的相对重要性。磁输运实验将探索分数量子霍尔区中量子霍尔态到绝缘体的转变和行为。磁光研究将用于表征InSb的能带结构，通过测量非掺杂势垒中的带间激子跃迁来确定限制势；通过分析激子跃迁、子带间共振和回旋共振来建立二维能带结构；以及探测低朗道能级填充的电子动力学。该项目的广泛范围需要三名合作研究人员之间的合作，他们在分子束外延、磁传输实验和光学测量方面拥有共同的专业知识。该项目解决了材料科学中具有很高潜在技术相关性的主题领域的基础研究问题。这项研究将在基础水平上为电子设备的新方面贡献基本的材料科学知识。在这些研究中将解决各种基本问题，拟议的实验还可能开发出具有重要技术意义的材料组合。该计划的一个重要特点是通过在一个具有根本意义和技术意义的领域对学生进行培训，将研究和教育结合起来。***

This project addresses materials science and physics of 2DES(two dimensional electronic systems) based on InSb/AlInSb heterostructures. InSb is characterized by extreme values compared to other III-V materials, having the smallest energy gap, the smallest electron effective mass, the largest electron g-factor, and the most non-parabolic conduction band of all III-V semiconductors. These dramatically different parameters make two-dimensional electronic systems (2DESs) in InSb intriguing alternatives to GaAs-based 2DESs. Although the host material can influence the physics of the imbedded 2DES, there has been little motivation to study 2DESs in alternative materials since most are of considerably worse crystalline quality. Now that InSb/AlxIn1-xSb structures have been produced with mobilities comparable to those of GaAs/AlxGa1-xAs structures in which the fractional quantum Hall effect was first observed. These high mobilities, coupled with the vastly different parameter space of InSb 2DESs, provide the impetus for this project. The objectives are to advance the materials science of InSb/AlxIn1-xSb heteroepitaxy and to explore the properties of InSb 2DESs via low-temperature magneto-transport and magneto-optics.Several approaches will be used to improve materials quality. A scanning probe microscope, connected to the same vacuum as the MBE chamber, will be used to assess doping efficiency and buffer layer effectiveness on lattice-mismatched substrates. An atomic hydrogen source will be used to passivate the growth surface and facilitate oxide desorption from InSb substrates. Improvement of the materials quality will increase the relative importance of electron-electron interactions in 2DESs studied at low temperature. Magneto-transport experiments will explore the quantum Hall state to insulator transition and behavior in the fractional quantum Hall regime. Magneto-optical studies will be used characterize the energy band structure of InSb to determine the confinement potential through measurement of interband excitonic transitions in undoped wells; establish the two-dimensional band structure through analysis of excitonic transitions, intersubband resonance, and cyclotron resonance; and probe electron dynamics at low Landau-level fillings. The wide scope of the project requires collaboration between three co-investigators with collective expertise in molecular beam epitaxy, magneto-transport experiments, and optical measurements. %%%The project addresses basic research issues in a topical area of materials science having high potential technological relevance. The research will contribute basic materials science knowledge at a fundamental level to new aspects of electronic devices. A variety of fundamental issues are to be addressed in these investigations, and the proposed experiments may also develop technologically important material combinations. An important feature of the program is the integration of research and education through the training of students in a fundamentally and technologically significant area. ***