Nanoscale Structure of Semiconductor Surfaces, Alloys, and Heterostructures

本项目研究半导体表面和界面的纳米级几何和电子结构。特别关注的是半导体合金的形成和性能，包括三元，例如In x Ga 1-x N，和四元，例如In x Ga 1-x As y p1 -y材料。将研究生长过程中合金成分的加入，以及原子有序、短程聚类和远距离合金成分波动（横向成分调制）的现象。离子注入和退火等外部扰动对组分变化的影响也将被研究。异质结构，包含具有不同晶格常数的材料层，将用于对材料施加应变。将观察该应变对所得合金成分和表面形貌的影响。这项研究的目的是阐明导致观察到的结构或成分变化的潜在微观机制，目的是设计改进的生长和/或加工技术，通过这些机制可以控制。用于这些研究的主要技术是扫描隧道显微镜（STM），它提供了表面上原子排列的纳米级信息。隧道显微镜的光谱研究将用于探测表面的电子态。研究将在平面视图模式下进行，在原位探测薄膜的生长表面，以及在异质结构被原位切割的横截面模式下进行。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材料科学的基础知识提供新的理解和电子/光子器件的能力。在这些调查中要解决各种基本问题。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 nanoscale geometric and electronic structure of semiconductor surfaces and interfaces. Particular focus is placed on the formation and properties of semiconductor alloys, including both ternary, e.g. In x Ga 1-x N, and quaternary, e.g. In x Ga 1-x As y P 1-y , materials. Incorporation of alloy constituents during growth will be studied, together with the phenomena of atomic ordering, short-range clustering, and long-range alloy compositional fluctuations (lateral composition modulation). The effect of external perturbations such as ion implantation and annealing on the compositional variations will also be examined. Heterostructures, containing layers of material with varying lattice constant, will be used to impose strain on the material. The effect of this strain on the resultant alloy composition and surface morphology will be observed. The intent of the research is to elucidate the underlying microscopic mechanisms responsible for the observed structural or compositional variations, with the aim of designing improved growth and/or processing techniques by which these mechanisms can be controlled. The major technique to be used for these studies is scanning tunneling microscopy (STM), which provides nanoscale information on the atomic arrangement on a surface. Spectroscopic studies with the tunneling microscope will be used to probe electronic states at the surface. Studies will be performed both in a plan-view mode, probing in situ the growth surface of films, as well as in cross-sectional mode in which a heterostructure is cleaved in situ. %%%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 understanding and capabilities in electronic/photonic devices. A variety of fundamental issues are to be addressed in these investigations. 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. ***