Growth of Low Defect Density III-Nitride Compounds on Nanowires

非技术描述：氮化镓光电器件是发展最快的领域之一，广泛用于固态照明、光学成像、扫描仪、功率放大器和开关，用于将可再生能源与电网连接。因此，它们的重要性是最令人关切的。成功提高材料质量的努力将提高器件性能，并影响多种工业和消费产品。技术优势：三族氮化物化合物是多种光学和电子器件的首选材料。 由于缺乏由二元和三元化合物制成的晶格匹配衬底和晶格匹配多层，目前III族氮化物化合物中存在高缺陷密度（约10 exp 9至10 exp 10/cm 2）。这些缺陷充当非辐射复合和散射中心，例如，影响少数载流子寿命并降低热导率。这些高缺陷密度限制了几种光电器件（例如紫外（UV）发光二极管（LED）、激光二极管以及功率器件和开关）的性能和可靠性。 以前减少这些缺陷的努力取得了有限的成功。本项目的目标是实现薄膜在III族氮化物化合物的缺陷密度低于10 exp 7/cm 2的整个晶圆。 整体方法涉及通过使用创新方法从纳米结构GaN模板过度生长。它开始于无掩模制造具有锥形尖端的纳米线，以促进过度生长的GaN膜的生长和合并。在纳米线结构上的早期过度生长阶段中，GaN在不同晶体刻面上的三维生长在剩余的位错相互作用中起着关键作用（因为位错湮灭和位错环形成的可能性大大增加）。 随后，在外延膜中产生嵌入空隙的网络，其充当位错汇。正在进行研究以确定减少缺陷的主要机制。 在本课题的研究过程中，本科生和研究生都参与了本课题的研究。 此外，外展计划包括本科生，少数民族学生和高中教师。

NON-TECHNICAL DESCRIPTION: Gallium nitride optoelectronic devices are amongst the fastest expanding fields and are being extensively used in solid-state lighting, optical imaging, scanners, power amplifiers and switches for interfacing renewable energy with the electric grid. Therefore, their importance is of the utmost concern. Efforts to successfully improve the material's quality will enhance device performance and impact several industrial and consumer products.TECHNICAL DETAILS: III-Nitride compounds are the material of choice in several optical and electronic devices. High defect densities (approximately 10exp9 to 10exp10 /cm2) are currently present in III-Nitride compounds due to the lack of both lattice matched substrates and lattice matched multilayers made from binary and ternary compounds. These defects act as non-radiative recombination and scattering centers that, for example, impact minority carrier lifetime and reduce thermal conductivity. These high defect densities limit the performance and reliability of several optoelectronic devices such as ultraviolet (UV) light-emitting diodes (LEDs), laser diodes as well as power devices and switches. Previous efforts to reduce these defects have had limited success. The objective of this project is to achieve films in III-nitride compounds with defect densities lower than 10exp7/cm2 over the entire wafer. The overall approach is involves overgrow from nanostructured GaN templates by using an innovative approach. It begins with a mask-less fabrication of nanowires with conical tips to facilitate the growth and coalescence of the overgrown GaN film. GaN three-dimensional growth on different crystallographic facets in early overgrowth stages on nanowire structures plays a key role in the remaining dislocation interactions (since the likelihood for dislocation annihilation and formation of dislocation loops are greatly increased). Subsequently a network of embedded voids in the epitaxial films are generated that act as dislocation sinks. Studies are underway to determine the dominant mechanism in the defects reduction. During the course of this project, both undergraduate and graduate students are engaged in the research. As well, the outreach program includes undergraduates, minority students, and high school teachers.