Collaborative Research: Analysis of Defects and Their Causes in Bulk Aluminum Nitride Crystals

合作研究：块状氮化铝晶体的缺陷及其原因分析

• 批准号: 0408874
• 负责人: James Edgar
• 金额: --
• 依托单位: Kansas State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-07-01 至 2008-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0408874&HistoricalAwards=false
• 关键词: Collaborative; Research; Analysis; Defects; Their

This project aims for greater understanding and control of defects associated with growth mechanisms of bulk aluminum nitride crystals produced by sublimation. Defects such as dislocations, stacking faults, grain boundaries, polytypoids and inversion domains will be correlated to impurities in crystals, growth conditions, and thermal and mechanical stresses. The types, densities, and the spatial distribution of defects will be measured by x-ray topography, transmission electron microscopy, defect selective etching, and decorative oxidation. Specific types of defects caused by oxygen and carbon will be determined. These impurities are typically present at relatively high concentrations (~1019 cm-3) in AlN crystals as a result of their high concentrations in the original source AlN powder, graphite heating elements, and furnace fixtures. The tendency for these elements to cause stacking faults, precipitates, and other defects will be investigated by comparing crystals with a broad range of impurity concentrations. Differences due to the crystal orientation and polarity will also be determined. The impact of temperature and nitrogen pressure on anisotropic growth rates and defects subsequently present in the crystals will be resolved. A series of crystals produced at different temperatures and nitrogen pressures will be examined to determine which defects are present, and their resulting influence on surface steps. Effects of sample mounting and other physical constraints on stress and subsequent spatial defect distribution will be examined. Residual stress in crystals will be measured and modeled. Surface and subsurface damage caused by mechanical action of polishing the AlN crystals will also be measured. Feedback from this information on defects in AlN is expected to allow the crystal growth process to be modified in a knowledgeable way so that crystal quality can be improved. %%% The project addresses fundamental research issues associated with electronic/photonic materials having technological relevance, and integrates research and educational activities. The project provides graduate students with unique opportunities to learn fundamental aspects of crystal growth and defect characterization. Through the established collaborations, students will be able to study research issues in greater depth than would be possible under separate investigations. Students will visit national laboratories, gain valuable experience working with state-of-the-art equipment and interacting with experienced scientists. The results of the research will be broadly disseminated by publication in high quality scientific journals and by organizing a materials research society symposium. Students will be actively involved by presenting their findings at professional society meetings. Workshops will be arranged for women and under represented group high school students to learn about AlN crystal growth and characterization. Principal investigators and their students will also visit middle school and high school to discuss this project, and to provide special encouragement to women and minority students to join science and engineering. ***

该项目旨在更好地了解和控制与升华法生产的块体氮化铝晶体的生长机制有关的缺陷。位错、层错、晶界、多型体和反转区等缺陷与晶体中的杂质、生长条件以及热应力和机械应力有关。缺陷的类型、密度和空间分布将通过X射线形貌术、透射电子显微镜、缺陷选择性刻蚀和装饰氧化来测量。将确定由氧和碳引起的特定类型的缺陷。这些杂质通常以相对较高的浓度(~1019 cm-3)存在于AlN晶体中，这是因为它们在原始的AlN粉末、石墨加热元件和炉具中的浓度很高。将通过比较具有广泛杂质浓度范围的晶体来研究这些元素引起堆积缺陷、沉淀和其他缺陷的倾向。由于晶体取向和极性的不同也将被确定。温度和氮气压力对晶体各向异性生长速度和随后出现的缺陷的影响将得到解决。将检查在不同温度和氮气压力下产生的一系列晶体，以确定存在哪些缺陷，以及它们对表面台阶的影响。样品安装和其他物理约束对应力和随后的空间缺陷分布的影响将被检查。晶体中的残余应力将被测量和建模。还将测量抛光氮化铝晶体的机械作用造成的表面和亚表面损伤。从这些关于氮化铝缺陷的信息中得到的反馈有望使晶体生长过程以一种有见地的方式进行修改，从而提高晶体质量。该项目解决与具有技术相关性的电子/光子材料相关的基础研究问题，并将研究和教育活动结合在一起。该项目为研究生提供了学习晶体生长和缺陷表征的基本方面的独特机会。通过已建立的合作，学生将能够比单独调查下更深入地研究研究问题。学生们将参观国家实验室，获得使用最先进设备和与经验丰富的科学家互动的宝贵经验。研究成果将通过在高质量的科学期刊上发表和组织材料研究会专题讨论会的方式广泛传播。学生将积极参与，在专业协会的会议上展示他们的发现。将为妇女和代表不足的群体高中生安排讲习班，以了解氮化铝晶体的生长和表征。主要研究人员和他们的学生还将访问初中和高中，讨论这一项目，并特别鼓励女性和少数民族学生加入理工科。***