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

Paskova, Tania M. (NCSU)：这项GOALI研究工作的目标是通过在不同衬底上使用氢化物气相外延实现可变缺陷密度的AlGaN合金的整个成分范围内的导热性进行系统研究，并探索点缺陷和结构缺陷在这些材料中的热输运中的作用。在与Kyma Technologies的合作中，我们的跨学科学术pi团队寻求获得对存在缺陷的热传递敏感性的理解，并开发适用于具有可变基材/层导热系数比的合金层的适当分析模型。目前，人们对开发基于iii -氮化物材料的紧凑高效器件非常感兴趣，用于各种电子和光电子应用。然而，大量缺陷的存在降低了器件的效率、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，但基于algan的器件的热管理还没有很好地发展，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。为了增强我们对这方面的知识并加速器件开发，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、缓冲液和层厚度来控制缺陷密度；（ii）确定了AlGaN合金导热系数的精确值及其与Al质量分数的关系，阐明了合金散射的影响；（iii）建立导热系数与位错和点缺陷密度的关系；（iv）氮化合金导热系数的理论建模，旨在验证或完善现有模型。采用多种技术进行微观结构表征，并采用3-omega方法测量AlGaN材料的导热系数。所获得的知识可以指导基于AlGaN三元合金的高期望氮化层和衬底的技术发展，以实现更好的器件结构热管理，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。该项目为研究生提供培训，通过课程开发、客座讲座、研讨会和Kyma的暑期实习，让他们接触到全面的、应用驱动的学术研究。该项目旨在让妇女和未被充分代表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将继续通过整合研究课题和成果在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.