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

技术摘要：这个材料世界网络项目的目标是研究在低成本的硅和蓝宝石衬底上生长非极性和半极性GaN的基本原理，目的是了解管理缺陷形成和成分/杂质结合的机制以及负责辐射复合的工艺。对缺陷形成机制的深入了解将使人们有可能设计出降低缺陷密度的方法，特别是层错和部分位错，并生产出具有更高亮度的发光二极管的高光学质量材料，并有可能用于激光二极管。非极性GaN中没有极化，而半极性GaN中的极化显著降低，将允许更高的复合效率，并消除发射能量对注入能级的依赖。在对优化的GaN薄膜中的光学基元、In和Mg掺杂以及Mg的激活能进行了明确的询问之后，我们将对非极性和半极性的InGaN/GaN和GaN/AlGaN量子阱和双异质结中的振子强度和辐射复合速率进行系统的研究，以回答这样一个关键问题：非极性和半极性的GaN取向有可能提供比极性的c平面GaN更高的发光效率。非技术概述：一个多机构/多学科的国际项目将汇集弗吉尼亚联邦大学在生长方面的独特专业知识、德国马格德堡大学丰富的精密光学测量能力以及法国蒙彼利埃大学在理论建模方面的丰富经验，以努力了解用于高效光发射器的变革性非极性和半极性氮化物半导体结构的合成和性质。这种方法将把急需的光投射到缺陷形成、杂质掺入和光学过程的基本原理中，从而为获得用于固态照明的明亮光源以及用于消费和军事应用的激光器和探测器奠定关键基础。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错综复杂的科学和软技能，以及接触美国、德国和法国的科学文化的额外好处。国际领先团体对研究生的交叉培养，本科生的研究经验，以及扩大中学生在材料科学和半导体器件领域的推广计划，将对培养未来的技能劳动力大有裨益。该项目得到了电子与光子材料项目和材料研究部特殊项目办公室的支持。

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.