GOALI: Thermal transport in AlGaN alloys: effect of point and structural defects

CBET-1336464PI：Paskova，Tania M.（NCSU）这GOALI研究工作的目标是进行AlGaN合金的热导率在整个组成范围内的可变缺陷密度通过使用氢化物气相外延在不同的衬底上实现了系统的研究，并探讨在这些材料的热输运点和结构缺陷的作用。在与Kyma Technologies的合作中，我们的跨学科学术PI团队寻求了解热传输对缺陷的敏感性，并开发适用于具有可变基底/层热导率比的合金层的适当分析模型。目前，人们对开发用于各种电子和光电应用的基于III族氮化物材料的紧凑且高效的器件非常感兴趣。然而，大量缺陷的存在降低了器件效率、光输出和寿命，同时导致过热。尽管它们具有巨大的实际重要性，但AlGaN基器件的热管理还没有得到很好的发展，并且热导率及其对通常存在的缺陷的依赖性的研究非常有限。为了提高我们对这一问题的认识，加速器件的发展，本研究项目的重点是：（i）生长优化，旨在通过改变生长条件、衬底、缓冲层和层厚度来控制缺陷密度;（ii）确定AlGaN合金的热导率的精确值及其对Al质量分数的依赖性，阐明合金散射的影响;（iii）建立热导率对位错和点缺陷密度的依赖关系;（iv）氮化物合金热导率的理论建模，旨在验证或改进现有模型。采用多种技术进行微结构表征，并使用3-omega方法测量AlGaN材料的热导率。所获得的知识可以指导基于AlGaN三元合金的高度期望的氮化物层和衬底的技术开发，以实现器件结构的更好的热管理，从而提高其性能和寿命，对于多种高功率，高频电子和高效光电应用至关重要。该项目的PI坚定地致力于研究和教育的整合。该项目通过课程开发、客座讲座、研讨会和Kyma暑期实习，让研究生接触全面的、应用驱动的学术研究，从而为研究生提供培训。该项目旨在让妇女和代表性不足的少数民族以及高中生参与并支持他们进行暑期科学研究。Kyma反过来将继续通过研究主题和结果的整合在NCSU获得曝光。

CBET-1336464PI: Paskova, Tania M. (NCSU)The objective of this GOALI research effort is to perform a systematic study of thermal conductivity of AlGaN alloys in the entire composition range with variable defect density achieved by using hydride vapor phase epitaxy on different substrates and to explore the role of point and structural defects on the thermal transport in these materials. In partnership with Kyma Technologies, our interdisciplinary team of academic PIs seeks to gain understanding of the thermal transport sensitivity to defect present and to develop a proper analytical model applicable to alloy layers with variable ratio of substrate/layer thermal conductivities. Currently, there is a considerable interest in developing compact and highly efficient devices based on III-Nitride materials for variety of electronic and optoelectronic applications. However, the presence of large number of defects reduces the device efficiency, light output and lifetimes while contributing to overheating. Despite their enormous practical importance, the thermal management of AlGaN-based devices is not well developed and the studies of thermal conductivity and their dependences on defects, typically present, are very limited. In order to enhanced our knowledge about that and to accelerate the device development this research project is focused on: (i) growth optimization, aiming to control the defect density by varying growth conditions, substrates, buffers, and layer thickness; (ii) determining the accurate values of thermal conductivity of AlGaN alloys and its dependence on the Al mass fraction, elucidating the effect of alloy scattering; (iii) establishing the thermal conductivity dependencies on both dislocation and point defect densities; (iv) theoretical modeling of thermal conductivity in nitride alloys, aiming to validate or refine the existing models. Variety of techniques is employed for the microstructure characterization, and the 3-omega method is used for the thermal conductivity measurements of the AlGaN materials. The knowledge gained can guide technological developments of highly desired nitride layers and substrates based on AlGaN ternary alloys to enable better thermal management of the device structures, and thus improving their performance and lifetime, being critically important for multiple high-power, high-frequency electronic and high-efficient optoelectronic applications. The PIs of this project are strongly committed to the integration of research and education. The project provides training of graduate students by exposing them to comprehensive, application-driven academic research through curriculum development, guest lectures, seminars and summer internships at Kyma. The project intends to involve and support women and underrepresented minorities, as well as high school students conducting summer science research. Kyma in turn will continue to receive exposure at NCSU through integration of the research topics and results.