Growth and Optical Properties of Nonpolar m-Plane GaN on Patterned Si and Sapphire Substrates

技术：本项目致力于用于GaN基器件的m平面GaN的材料科学合成/工艺研究。GaN基材料在c面上是高度极性的，当应变存在或引入成分梯度时，会产生极化电荷。随之而来的斯塔克漂移降低了辐射复合效率，并可能导致发光二极管(LED)中的载流子泄漏，从而降低其效率。研究的重点将是外延m平面GaN的合成和光学过程的研究。随之而来的一个目标是探索在相对低成本的图案化蓝宝石和硅衬底上生长排列良好的m平面GaN薄膜，以了解其中涉及的生长机制的基本原理。非极性m平面GaN合成的基础研究将与必要的表征结合在一起进行，以进一步了解这些层中的辐射复合过程。我们将使用结构、电学和光学表征技术来研究薄膜的取向和形貌，以及延伸缺陷和点缺陷。其目的是探索在低成本的蓝宝石和刻蚀的硅衬底上合成m平面GaN的科学基础。此外，还将研究光学矩阵元素的增强，m平面取向外延层中p型电导率的增强，以及在没有偏振场的情况下量子限制效应及其对光学效率的影响的基础研究。非技术性：本项目是在材料科学的一个具有高度技术相关性的热门领域中的基础研究问题。研究成果可能为更高效的发光二极管(如具有可接受的显色指数和固态照明效率的LED)铺平道路。这些研究有可能生产出用于固态照明应用的足够明亮的光源，以及用于消费和军事应用的激光和探测器。这项研究对于确保美国保持目前在探索和实施技术方面的领先地位具有重要意义，这些技术将带来能源节约和随之而来的环境效益。该项目还将研究和教育融为一体。PIS为电气工程和物理领域的研究生和本科生建立了一个协作和跨学科的研究环境，该项目将为研究生和本科生提供宝贵的跨学科学习机会，与国际科学家互动，发展产业联系，并帮助他们教育和理解半导体技术和物理的基础知识。学生们还参与了PIs通过帮助实现基于半导体的高效白光发电来减少温室气体排放的努力。由于VCU是一所不断发展的城市大学，学生群体多样化(18%非裔美国人，22%其他少数族裔)，私人投资机构从相对较大的来自代表性不足的群体的学生中招聘学生。因此，他们在自己的实验室里建立了少数族裔学生，并将继续解决多样性问题。

Technical: This project addresses materials science synthesis/processing research of m-plane GaN for use in GaN-based devices. GaN-based materials are higly polar on c-plane which when strain is present or a compositional gradient is introduced resulting in polarization charge. The ensuing Stark shift reduces radiative recombination efficiency and can cause carrier leakage in light emitting diodes (LEDs) reducing their efficiency. The research emphasis will be on synthesis of epitaxial m-plane GaN and investigation of optical processes. An accompanying aim is to explore growth of well-aligned, m-plane GaN films on relatively low cost patterned sapphire and Si substrates to understand the fundamentals of growth mechanisms involved. A basic investigation of non polar m-plane GaN synthesis on inexpensive and readily available, but appropriately patterned substrates will be carried out in conjunction with requisite characterization to gain further understanding on radiative recombination processes in such layers. The orientation and morphology of the films, as well as extended and point defects will be investigated using structural, electrical, and optical characterization techniques. The objective is to explore the science underlying the synthesis of m-plane GaN on low-cost sapphire and Si substrates with etched facets. Additionally, the enhancement of optical matrix elements, p-type conductivity in m-plane oriented epitaxial layers, and basic investigation of quantum confinement effects and their influence on the optical efficiency in the absence of polarization fields will be studied.Non-technical: This project addresses basic research issues in a topical area of materials science with high technological relevance. The research outcomes could pave the way for more efficient light emitters such as LEDs with acceptable color rendering index and efficacy for solid state lighting. These investigations have the potential to produce sufficiently bright light sources for solid state lighting applications, as well as lasers and detectors for consumer and military applications. The research is important in ensuring that the US maintains its current status as a leader in the exploration and implementation of technologies that will lead to energy savings and concomitant environmental benefits. The project also integrates research and education. The PIs have established a collaborative and interdisciplinary research environment for graduate and undergraduate students from electrical engineering and physics fields, and this project will provide graduate and undergraduate students opportunities for valuable cross-disciplinary learning, for interactions with international scientists, for development of industrial connections, in addition to assisting their education and understanding of fundamentals of semiconductor technology and physics. Students are also involved in the PIs' efforts toward reduced green house gas emission by helping to achieve semiconductor based efficient white light generation. Since VCU is a growing urban university with a diverse student body (18% African American, 22% other minorities), the PIs recruit from a relatively large pool of students from underrepresented groups. Consequently, they have established minority students in their laboratories and will continue to address diversity.