FRG: Morphological Electronic and Chemical Structure of Lattice-Mismatched III-V Heterojunctions

这个FRG项目涉及一组跨学科的PI，以探索决定晶格失配异质结最终器件生存能力的基本属性。晶格失配不仅决定生长形态，而且影响热力学稳定性、局域电子态的产生和带边不连续处的输运势垒。晶格匹配技术晶格失配材料可以在原子尺度上操纵电子和光学性质。对这些问题的控制可能会消除标准材料(例如，GaAs和InP)对各种半导体材料所能实现的功能的限制。可感知的挑战是在同时控制机械、化学和电子结构的情况下实现平面生长和热兼容性。必须在基本水平上理解这些性质和生长参数之间的相互关系，才能显著提高晶格失配异质结构的利用率。该项目不仅努力了解每一组特性，而且还努力发现它们是如何因生长条件的特定变化而产生的。该方法包括(I)通过分子束外延(MBE)生长，(Ii)直接测量所创建材料的原子结构，(Iii)电子、原子尺度和光学性质的原位和非原位测量，以及(Iv)实际材料的电子结构的理论计算。选择了几个基于III-V化合物的模型系统，既是因为这些材料系统在先进设备中的技术重要性，也是作为解释测量和计算所需的精确控制样本集。该项目的重点主要是在InP、InGaP和InAlP上生长的InAlAs、InGaP和InAsP失配异质结，以及几种不同失配的选择二元组合，以提供精确控制的测量数据，以便与理论性质计算相关联。%该项目解决了材料科学中具有高度技术相关性的主题领域的基础研究问题。该项目建立在典型异质结系统的最新进展的基础上，同时增加了表征失配薄膜随着生长而演变的电子性质的新能力。从研究中获得的基本知识和理解有望有助于提高半导体材料在当前和未来器件和电路应用中的性能。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。这个FRG项目的多学科性质(材料科学、电气工程、物理)为学生提供了独特的教育机会，让他们体验以团队合作为导向的研究环境。***

This FRG project involves a cross-disciplinary group of PIs to explore underlying properties that dictate ultimate device-viability of lattice-mismatched heterojunctions. Lattice mismatch not only determines the growth morphology but also affects thermodynamic stability, creation of localized electronic states, and transport barriers at band edge discontinuities. Techniques for lattice matching lattice-mismatched materials can manipulate electronic and optical properties on an atomic scale. Control of these issues may remove constraints imposed by standard materials (e.g., GaAs and InP) on the functionality attainable from the full range of semiconductor materials. The perceived challenges are to achieve planar growth and thermal compatibility with simultaneous control of mechanical, chemical, and electronic structure. The inter-relationships between these properties and growth parameters must be understood at a fundamental level to achieve significantly greater utilization of lattice-mismatched heterostructures. The project strives to not only understand each set of properties, but also to discover how they result from specific variations in growth conditions. The approach incorporates (i) growth by molecular beam epitaxy (MBE), (ii) direct measurement of the atomic structure of the created materials, (iii) in-situ and ex-situ measurements of electronic, atomic-scale and optical properties, and (iv) theoretical calculations of electronic structure of the actual materials. A few model systems based on III-V compounds were chosen both for the technological importance of these material systems in advanced devices and as precisely controlled sample sets necessary to interpret the measurements and calculations. The project focus is primarily on InAlAs, InGaAs and InAsP mismatched heterostructures grown on InP, InGaP and InAlP grown on GaAs, and a few choice binary combinations of varying misfit to provide precisely controlled measurement data for correlation with theoretical calculations of properties. %%%The project addresses basic research issues in a topical area of materials science with high technological relevance. The project builds on recent advances in representative heterojunction systems, while adding new capabilities for characterizing electronic properties of mismatched films as they evolve with growth. The basic knowledge and understanding gained from the research is expected to contribute to improving semiconductor materials performance in current and future device and circuit applications. 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. The multidisciplinary (materials science, electrical engineering, physics) nature of this FRG project offers unique educational opportunities for students to experience a teamwork-oriented research environment. ***