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

技术：该项目致力于用于GaN基器件的m面GaN的材料科学合成/加工研究。GaN基材料在c平面上是高极性的，当存在应变或引入组分梯度时，导致极化电荷。随之而来的斯塔克位移降低了辐射复合效率，并且可能导致发光二极管（LED）中的载流子泄漏，从而降低其效率。本研究将着重于磊晶m面氮化镓之合成及光学制程之研究。伴随的目的是探索在相对低成本的图案化蓝宝石和Si衬底上良好对准的m面GaN膜的生长，以了解所涉及的生长机制的基本原理。非极性m-平面GaN合成的廉价和容易获得的，但适当的图案化基板的基本调查将进行必要的表征，以获得进一步了解在这样的层的辐射复合过程。薄膜的取向和形态，以及扩展和点缺陷将使用结构，电学和光学表征技术进行研究。目的是探索在低成本蓝宝石和Si衬底上合成m面GaN的科学基础。此外，还将研究光学矩阵元素的增强、m面取向外延层中的p型导电性、量子限制效应的基础研究及其在没有偏振场的情况下对光学效率的影响。非技术性：本项目涉及具有高技术相关性的材料科学领域的基础研究问题。研究成果可以为更高效的光发射器铺平道路，例如具有可接受的显色指数和固态照明功效的LED。这些研究有可能为固态照明应用产生足够亮的光源，以及为消费者和军事应用产生激光器和探测器。这项研究对于确保美国保持其目前在探索和实施技术方面的领导地位至关重要，这些技术将导致节能和伴随的环境效益。该项目还整合了研究和教育。PI为来自电气工程和物理领域的研究生和本科生建立了一个合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，与国际科学家进行互动，发展工业联系，除了帮助他们的教育和半导体技术和物理的基础知识的理解。学生们还参与了PI通过帮助实现基于半导体的高效白色光发电来减少绿色气体排放的努力。由于VCU是一所不断发展的城市大学，拥有多元化的学生群体（18%的非裔美国人，22%的其他少数民族），PI从代表性不足的群体中招募相对较大的学生。因此，他们在实验室里培养了少数民族学生，并将继续处理多样性问题。

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.