Understanding Microstructures of Mixed Group III-Nitride Layers

本项目旨在全面了解III族氮化物混合层的微观结构，旨在促进对这些材料中相分离和原子有序化发生的理解。将进行实验，以辨别相分离是在体相还是在表面发生。方法是研究生长速度和生长温度对相分离微结构的影响。将进行内扩散实验，以评估这些微结构是否代表块体中的平衡状态。原子有序的起源将通过在[110]微面GaN层上生长混合层来研究，以确定这些面在原子有序化中的作用。将检查不同有序区之间的界面和以不同生长速度生长的层中有序域的分布。此外，还将通过霍尔测量来评估相分离和原子有序对载流子迁移率的影响。这些研究将利用InGaN和AlGaN层，也可能包括AlInN和AlInGaN薄膜。薄膜的生长将使用金属有机化学气相沉积和分子束外延。显微结构将用常规和高分辨率的X射线衍射和透射电子显微镜进行研究。能量损失光谱，结合能量过滤成像，将被用来研究原子物种在层中的分布。该项目涉及与技术相关的电子材料科学领域的基础研究问题。预计这项研究将对第三族氮化物材料和器件的科学和技术产生重大影响。该项目的一个重要特点是高度重视教育，研究与教育相结合。可利用的资源为从事跨学科前沿研究的研究生提供了特殊的教育和培训机会。

This project aims for a comprehensive understanding of microstructures of mixed group III-nitride layers, intending to advance understanding of the occurrence of phase separation and atomic ordering in these materials. Experiments to discern whether or not phase separation oc-curs in the bulk or on the surface will be conducted. The approach is to examine the effects of growth rates and growth temperatures on phase-separated microstructures. In-diffusion experi-ments to evaluate whether or not these microstructures represent the equilibrium state in the bulk will be carried out. The origins of atomic ordering will be studied through growth of mixed lay-ers on [ 1 1 10 ] microfaceted GaN layers to ascertain the role of these facets in atomic ordering. Interfaces between differently ordered regions and distribution of ordered domains in layers that have been grown at different growth rates will be examined. Additionally, the influence of phase separation and atomic ordering on carrier mobility by Hall measurements will be evaluated. These studies will utilize InGaN and AlGaN layers, and may also include AlInN and AlInGaN films. Film growth will be done using metalorganic chemical vapor deposition and molecular beam epitaxy. Microstructures will be studied by X-ray diffraction and transmission electron mi-croscopy, both conventional and high resolution. Energy loss spectroscopy, coupled with energy filtered imaging, will be utilized to study the distribution of atomic species in layers. %%% The project addresses fundamental research issues in areas of electronic materials science having technological relevance. It is envisaged that this research could have a significant impact on sci-ence and technology of group III-nitride materials and devices. An important feature of the proj-ect is the strong emphasis on education, and the integration of research and education. The avail-able resources provide special opportunities for education and training of graduate students in-volved in interdisciplinary forefront research.***