A search for novel efficient p-type nitride materials

非技术描述：氮化镓(GaN)半导体是用于固态照明和其他电子应用的明亮发光二极管(LED)的关键组件。这些器件中的大多数依赖于所谓的p型GaN，这是一种添加了杂质的材料，大大改善了其性能。此外，光电子学中令人兴奋的机会目前出现在相关材料p型AlGaN的开发中。这可能具有开创性，因为它将为明亮的紫外线(UV)LED铺平道路，这些LED可用于多种节能应用，包括空气和水净化、光疗、气体传感、植物生长照明和UV固化。本实验/理论研究项目旨在实现新型高效导电p型GaN和AlGaN半导体材料。在GaN和AlGaN中添加Be杂质有望显著改善这些材料的p型电导率，从而显著提高UV LED的效率。学生，包括那些来自代表性不足的群体的学生，有机会获得最先进的材料沉积、光学光谱实验和理论计算的实践经验。该项目还为弗吉尼亚联邦大学一个相对较小的物理系的研究和教育奠定了坚实的基础。技术描述：该项目致力于Be掺杂GaN和AlGaN的生长以及这些材料中点缺陷的基础研究。对掺Be GaN的光致发光分析表明，Be是GaN中最浅的受主，但实现p型电导仍然是一个具有挑战性的任务，因为在材料生长过程中会形成各种点缺陷。这项合作研究包括第一性原理计算Be的微观性质和GaN和AlGaN中的相关缺陷，用金属有机化学气相沉积方法生长Be掺杂的GaN和AlGaN，使用离子注入，热退火，以及详细的实验研究，主要是用光致发光和开尔文探针法。研究了生长条件(温度、压力、气氛)、Si、Mg共掺杂、Delta掺杂技术、表面活性剂的使用、不同的热退火方法对获得导电p型材料的影响。利用先进的实验和理论手段对Be和其他缺陷在GaN和AlGaN中的性质和行为进行深入和全面的研究，对于基本了解半导体中的点缺陷，辐射和非辐射复合的机制，以及实现高效p型材料的可能的生长途径是必不可少的。此外，固态理论中当前方法的准确性通过直接的实验验证进行了严格的检验。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical Description: Gallium nitride (GaN) semiconductor is a key component in bright light-emitting diodes (LEDs) used in solid-state lighting and other electronics applications. Most of these devices rely on so-called p-type GaN, a material with added impurities, which greatly improve its properties. In addition, exciting opportunities in optoelectronics currently emerge in development of a related material, p-type AlGaN. This is potentially groundbreaking since it will pave the way toward bright ultraviolet (UV) LEDs that can be used in numerous energy efficient applications, including air and water purification, phototherapy, gas sensing, plant growth lighting, and UV curing. The integrated experiment/theory research project is aimed at realizing new efficient conductive p-type GaN and AlGaN semiconductor materials. Adding beryllium (Be) impurity to GaN and AlGaN is expected to result in significantly improved p-type conductivity of these materials, leading to dramatic improvement of UV LED efficiency. Students, including those from underrepresented groups, have the opportunity to gain hands-on experience with state-of-the-art material deposition, optical spectroscopy experiments, and theoretical calculations. The project also builds a strong foundation for research and education in a relatively small Physics Department at Virginia Commonwealth University. Technical Description: The project focuses on growth of Be-doped GaN and AlGaN and fundamental studies of point defects in these materials. Analysis of photoluminescence from Be-doped GaN indicates that Be is the shallowest acceptor in GaN, yet achievement of p-type conductivity is still a challenging task, because a variety of point defects are formed during material growth. This collaborative research involves first-principles calculations of microscopic properties of Be and related defects in GaN and AlGaN, growth of Be-doped GaN and AlGaN by metalorganic chemical vapor deposition method, use of ion implantation, thermal annealing, and detailed experimental studies, primarily with photoluminescence and Kelvin probe methods. The roles of growth conditions (temperature, pressure, gas ambient), co-doping with Si and Mg, delta doping techniques, use of surfactants, various thermal annealing approaches are investigated to achieve conductive p-type materials. An in-depth and comprehensive study of the properties and behavior of Be and other defects in GaN and AlGaN by using advanced experimental and theoretical approaches is essential to gain a basic understanding of point defects in semiconductors, the mechanisms of radiative and nonradiative recombination, and possible growth pathways for realizing the efficient p-type materials. Furthermore, the accuracy of current approaches in solid-state theory is critically examined through direct experimental verification.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.