Electronic Properties of Strained Narrow-Gap Quantum Wells

本项目研究基于InSb/AlInSb异质结构的2DES（二维电子系统）材料科学和物理学。与其他III-V类材料相比，InSb具有极值的特点，在所有III-V类半导体中具有最小的能隙、最小的电子有效质量、最大的电子g因子和最多的非抛物线导带。这些显著不同的参数使InSb中的二维电子系统（2DESs）成为基于砷化镓的二维电子系统的有趣替代方案。虽然主体材料可以影响嵌入2DES的物理性质，但由于大多数材料的晶体质量相当差，因此很少有动力研究替代材料中的2DES。现在已经产生了InSb/AlxIn1-xSb结构，其迁移率与首次观察到分数量子霍尔效应的GaAs/AlxGa1-xAs结构相当。这些高机动性，加上InSb 2DESs的巨大不同的参数空间，为这个项目提供了动力。目的是推进InSb/AlxIn1-xSb异质外延的材料科学，并通过低温磁输运和磁光学探索InSb 2DESs的性能。将采用几种方法来提高材料质量。扫描探针显微镜连接到与MBE腔室相同的真空中，将用于评估晶格不匹配衬底上的掺杂效率和缓冲层的有效性。原子氢源将用于钝化生长表面，并促进从InSb底物上的氧化物解吸。随着材料质量的提高，电子-电子相互作用在低温下的研究将变得更加重要。磁输运实验将探索分数量子霍尔态到绝缘体的跃迁和行为。磁光研究将用于表征InSb的能带结构，通过测量未掺杂阱中的带间激子跃迁来确定约束势；通过分析激子跃迁、子带间共振和回旋共振，建立二维能带结构；探测低朗道能级充填的电子动力学。该项目范围广泛，需要三位共同研究人员在分子束外延、磁输运实验和光学测量方面进行合作。该项目涉及具有高潜在技术相关性的材料科学主题领域的基础研究问题。该研究将在基础层面上为电子器件的新方面贡献基础材料科学知识。在这些研究中要解决各种基本问题，并且提出的实验也可能发展技术上重要的材料组合。该计划的一个重要特点是通过培养学生在一个基础和技术上重要的领域的研究和教育的整合。＊＊＊

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. ***