FRG: Nanopatterning of Sapphire Substrates for Improved III-Nitride Growth

FRG：蓝宝石衬底的纳米图案化以改善 III 族氮化物的生长

• 批准号: 0705299
• 负责人: Helen Chan
• 金额: $ 32万
• 依托单位: Lehigh University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-09-01 至 2009-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0705299&HistoricalAwards=false
• 关键词: FRG; Nanopatterning; Sapphire; Substrates; Improved

NON-TECHNICAL DESCRIPTION: In the fabrication of optical devices such as lasers and light emitting diodes (LEDs), sapphire is used as the underlying material for the growth of GaN (and related semiconductor materials). Over the course of the project, new types of processes will be developed which can be used to produce a patterned structure on the surface of a sapphire crystal, with feature sizes at the nanometer level. The presence of the patterned features enables a greater degree of crystalline perfection in the GaN, which in turn leads to devices which are brighter, that last longer and are more energy efficient. Such solid state light sources can result in overall cost-savings, and potentially replace traditional incandescent bulbs for many applications. Opportunities for research involvement at the high school and college level are planned, as well as local and community outreach through an NSF-funded Nanoscale Informal Science Education Network. TECHNICAL DETAILS: The aim of the project is to achieve higher luminescence efficiency in GaN LEDs by exploiting a novel process (AGOG) for surface patterning of sapphire substrates. The work builds on prior work which showed that heat-treatment of a planar metallic Al film (thickness ~100 nm) deposited on a sapphire surface can lead to epitaxial conversion. A key advantage of the AGOG conversion procedure is that compared to currently available methods, it is relatively amenable to modification of both surface chemistry and morphology. Several new and hitherto unexplored strategies for enhancing the optical efficiency of blue LED devices are under investigation. These include: a) Patterning of the metallic coating (prior to conversion) into an array of nanoscale mesas (width 50 - 150 nm, height ~100 nm) to increase the compliance of the surface regions, and hence reduce the density of misfit dislocations arising from the lattice mismatch between GaN and sapphire, b) Growth of non-polar GaN by utilizing a patterned sapphire substrate with r-plane orientation, and c) Reducing the lattice mismatch by up to 30% by fabricating mesas with additions of chromia. Fundamental issues with regard to Al oxidation mechanisms and morphological stability at the nanoscale are also being addressed. Clearly diffusional processes which take place at the surface or along the Al/sapphire interface will become increasingly important as the feature size decreases. This may involve mechanisms and/or transformation kinetics which diverge significantly from bulk behavior.

非技术描述：在制造光学设备（例如激光器和发光二极管（LED））中，蓝宝石用作GAN生长的基础材料（以及相关的半导体材料）。在项目的整个过程中，将开发出新的过程，可用于在蓝宝石晶体的表面产生图案结构，并在纳米级上具有特征大小。 图案化特征的存在使GAN中具有更大程度的结晶完美，这又导致更明亮的设备，持续时间更长，更节能。 这样的固态光源可能会导致整体成本节省，并有可能替代许多应用的传统白炽灯泡。 计划通过NSF资助的纳米级非正式科学教育网络，计划在高中和大学一级进行研究的机会，以及本地和社区宣传的机会。技术细节：该项目的目的是通过利用新颖的过程（AGOG）来实现GAN LED的更高发光效率，以实现蓝宝石底物的表面图案。 这项工作是基于先前的工作，表明沉积在蓝宝石表面上的平面金属膜（厚度约100 nm）的热处理会导致外延转换。 AGOG转换程序的关键优势是与当前可用的方法相比，它相对适合修饰表面化学和形态。 正在研究一些新的和迄今未开发的策略，以提高蓝色LED设备的光学效率。 其中包括：a）将金属涂层（转换之前）构图为一系列纳米级膜（宽度50-150 nm，高度〜100 nm），以提高表面区域的依从性，从而减少与甘台和sapph sapph sapph sapph saplate a Proventate a Proffort a Plate a Plate a Plate a Plate a Proffite a Plate a Proffite a Plate a Proffite a plate a plate a plate a plotial a plate a plotial a py al pli al s a ply a plotial a plotial b）的依从性的密度。 R平面取向，C）通过加入Chromia来制造Mesas，将晶格不匹配最多减少30％。 关于纳米级的Al氧化机制和形态稳定性方面的基本问题也正在解决。 显然，随着特征大小的减小，在表面或沿Al/Sapphire界面进行的扩散过程将变得越来越重要。 这可能涉及机制和/或转化动力学，这些动力学与批量行为显着不同。