Materials World Network: Investigation of Nonpolar and Semipolar GaN on Si and Sapphire: Optical Processes and Efficiency

技术概述：这个材料世界网络项目的目标是研究在低成本Si和蓝宝石衬底上非极性和半极性GaN生长的基本原理，目的是了解控制缺陷形成和成分/杂质掺入的机制，以及负责辐射重组的过程。对缺陷形成机制的深入了解将使设计降低缺陷密度的方法成为可能，特别是堆积错误和部分位错，并为具有增强亮度的发光二极管和潜在的激光二极管生产高光学质量的材料。非极性氮化镓中极化的缺失和半极性氮化镓中极化的大幅降低将允许更高的重组效率，并消除发射能量对注入水平的依赖。在对优化后的GaN薄膜中的光学矩阵元素、In和Mg的掺杂以及Mg的活化能进行了清晰的研究之后，将对非极性和半极性InGaN/GaN和GaN/AlGaN量子阱以及双异质结构中的振荡器强度和辐射复合率进行系统的研究，以回答非极性和半极性GaN取向比极性c面GaN具有更高效率的光发射体的关键问题。非技术总结：这是一个多机构/多学科的国际项目，汇集了弗吉尼亚联邦大学在增长方面的独特专业知识，德国马格德堡大学精密光学测量的广泛能力，并将在蒙彼利埃大学（法国）进行理论建模，以努力了解用于高效光发射器的转化非极性和半极性氮化物半导体结构的合成和特性。这种方法将为缺陷形成、杂质掺入和光学过程的基本原理提供急需的光，因此将为获得用于固态照明的明亮光源以及用于消费者和军事应用的激光器和探测器奠定关键的基础。这个材料世界网络项目将为材料科学、工程和半导体理论提供广阔的视角，并为研究生和本科生提供肥沃的土壤，教授他们在全球网络纳米技术劳动力中取得成功所必需的复杂科学和软技能，并为他们提供接触美国、德国和法国科学文化的额外好处。在材料科学和半导体器件领域，通过国际领先组织对研究生进行交叉培训，为本科生提供研究经验，并扩大中学生的外展计划，将对培养未来的熟练劳动力大有帮助。本项目由电子与光子材料项目和材料研究部特殊项目办公室支持。

TECHNICAL SUMMARY: The objective of this Materials World Network project is to investigate the fundamentals of nonpolar and semipolar GaN growth on low cost Si and sapphire substrates with the aim of understanding the mechanisms governing defect formation and constituent/impurity incorporation as well as processes responsible for radiative recombination. Insight into mechanisms responsible for the defect formation will make it possible to devise approaches for reducing the defect density, particularly the stacking faults and partial dislocations, and produce high-optical-quality material for light-emitting diodes with enhanced brightness and potentially for laser diodes. The absence of polarization in nonpolar GaN and substantially reduced polarization in semipolar GaN will allow higher recombination efficiencies and eliminate the dependence of emission energy on injection level. After interrogating cleanly the optical matrix elements, In and Mg incorporation, and Mg activation energy in optimized GaN films, systematic studies of oscillator strengths and radiative recombination rates in nonpolar and semipolar InGaN/GaN and GaN/AlGaN quantum wells and double heterostructures will be undertaken to answer the critical question which non-polar and semipolar GaN orientation has the potential to provide higher efficiency light emitters than polar c-plane GaN. NON-TECHNICAL SUMMARY:A multi-institutional/multidisciplinary international program bringing together the unique expertise in growth, available at the Virginia Commonwealth University, extensive capabilities of precise optical measurements at the University of Magdeburg (Germany), and demonstrated experience in theoretical modeling at the University of Montpellier 2 (France) will be undertaken in an effort to understand the synthesis and properties of transformative nonpolar and semipolar nitride semiconductor structures for high efficiency light emitters. This approach will shed the much needed light into the fundamentals of defect formation, impurity incorporation, and optical processes and thus will lay the critical groundwork for attainment of bright light sources for solid-state lighting, as well as lasers and detectors for consumer and military applications. This Materials World Network project will allow a broad perspective of materials science, engineering, and semiconductor theory and provide a fertile ground for teaching graduate and undergraduate students the intricacies of science and soft skills necessary for success in the global, cyber-enabled nanotechnology workforce, with the additional benefit of exposure to cultures of science in the US, Germany, and France. Cross training of graduate students by leading international groups, research experiences for undergraduate students, and expansion of outreach programs for middle school students in the fields of materials science and semiconductor devices will go a long way for training the future skilled workforce.This project is supported by the Electronic and Photonic Materials program and Office of Special Programs, Division of Materials Research.