GOALI: Thermal Transport by Phonons in Device-Grade Nitride Nanostructures

GOALI：设备级氮化物纳米结构中声子的热传输

• 批准号: 1133394
• 负责人: Jonathan Malen
• 金额: $ 39.53万
• 依托单位: Carnegie-Mellon University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-01 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1133394&HistoricalAwards=false
• 关键词: GOALI; Thermal; Transport; Phonons; Device

PI: Jonathan A. MalenProposal Number: 1133394Nitride-based semiconductors are a centerpiece of light-emitting diodes (LEDs) for solid-state lighting, select high-frequency/power electronics, and future multi-junction photovoltaics. Progress towards commercialization of these technologies demands high current densities that compel improved thermal management to lower operating temperatures. While packaging strategies improve heat dissipation, preliminary data show that the device itself has a large thermal resistance. Thermal conductivity (k) measurements on device-grade nitride films show very low values of k in thin 100nm aluminum nitride (AlN) and 100nm gallium nitride (GaN) layers. Electron microscopy images suggest that these reductions are caused by structural imperfections inherent to industrial growth processes. As yet, a clear scientific explanation is lacking.Intellectual Merit: The objective of this GOALI proposal is to study thermal transport in nitride semiconductor heterostructures composed of GaN, AlN, and indium gallium nitride (InGaN) thin films (~100nm), fabricated by scalable growth processes. An interdisciplinary team of academic investigators at Carnegie Mellon University (CMU), in partnership with Kyma Technologies, will study the nature of thermal transport by phonons in nitride nanostructures. Defective films and interfaces separated by distances commensurate to the bulk phonon mean free paths will be considered. Open scientific questions include: What is the thermal boundary resistance (R) at the device-substrate interface and between nitride layers? Can highly defective crystals transport heat in a manner similar to disordered materials? How do growth techniques impact thin film thermal properties?To answer these questions, the investigation will focus on a common base structure that includes a sapphire, silicon carbide, or GaN substrate with an AlN nucleation layer followed by an InGaN buffer layer. Specific inquiries include: (i) the effect of the substrate on R and k of the AlN nucleation layer, (ii) the effect of growth technique on k and R of the AlN nucleation layer, and (iii) the effect of indium concentration on k and R of the InGaN buffer layer. Controlled growth of nitrides and imaging of defect density and structure (Davis, Paskova) will be used to inform the atomic structure for molecular dynamics simulations (McGaughey). Simulation results will be compared with direct measurements of k and R on these samples, made using a pump-probe optical method called Frequency Domain Thermoreflectance (Malen).Broader Impact: Partnership with Kyma Technologies makes this research directly transferable to industry, where nitride devices have the potential to revolutionize lighting and to outperform silicon-based electronics. Kyma recognizes the critical need for incorporating thermal-management into the nitride device structure. Access to Kyma's growth technologies, which represent the future of nitrides, will make any discoveries far-reaching. Continuing collaborations on nitride science and technology with the Cree Corporation and the Naval Research Laboratory further support the need for this research. The educational activities will expose students to industry-driven academic research through curriculum development, guest lectures and seminars, and summer internships at Kyma. Kyma, in turn, will receive exposure at CMU through integration of the research topics and results within courses taught by the academic PIs. An LED-based outreach activity "Lighting: The Next Generation" will be developed for the Society of Women Engineers High School Day, Pittsburgh public schools, and the YWCA TechGyrls program.

PI：Jonathan A. Malen提案编号：1133394氮化物基半导体是固态照明、选择高频/电力电子和未来多结光电子的发光二极管（LED）的核心。这些技术商业化的进展需要高电流密度，这迫使改进热管理以降低操作温度。虽然封装策略改善了散热，但初步数据显示，器件本身具有较大的热阻。器件级氮化物薄膜的热导率（k）测量显示，100 nm氮化铝（AlN）和100 nm氮化镓（GaN）薄层的k值非常低。电子显微镜图像表明，这些减少是由于工业增长过程中固有的结构缺陷。智力上的优点：GOALI的目标是研究氮化物半导体异质结构中的热输运，该异质结构由GaN、AlN和氮化铟镓（InGaN）薄膜（~ 100 nm）组成，通过可扩展的生长工艺制造。卡内基梅隆大学（CMU）的一个跨学科学术研究团队与Kyma Technologies合作，将研究氮化物纳米结构中声子的热传输性质。有缺陷的薄膜和界面分离的距离相称的体声子平均自由程将被考虑。公开的科学问题包括：器件-衬底界面和氮化物层之间的边界热阻（R）是多少？高度缺陷的晶体能以类似于无序材料的方式传热吗？生长技术如何影响薄膜的热性能？为了回答这些问题，调查将集中在一个共同的基础结构，包括蓝宝石，碳化硅，或GaN衬底与氮化铝成核层，其次是InGaN缓冲层。具体查询包括：（i）衬底对AlN成核层的R和k的影响，（ii）生长技术对AlN成核层的k和R的影响，以及（iii）铟浓度对InGaN缓冲层的k和R的影响。氮化物的受控生长以及缺陷密度和结构的成像（Davis，Paskova）将用于为分子动力学模拟（McGaughey）提供原子结构信息。模拟结果将与使用称为频域热反射（Malen）的泵浦-探测光学方法对这些样品进行的k和R直接测量进行比较。更广泛的影响：与Kyma Technologies的合作使这项研究可以直接应用于工业，氮化物器件有可能彻底改变照明并超越硅基电子产品。 Kyma认识到将热管理纳入氮化物器件结构的迫切需要。Kyma的生长技术代表了氮化物的未来，将使任何发现都具有深远的意义。与Cree公司和海军研究实验室在氮化物科学和技术方面的持续合作进一步支持了这项研究的需要。教育活动将通过课程开发，客座讲座和研讨会以及Kyma的暑期实习让学生接触行业驱动的学术研究。Kyma反过来将通过整合学术PI教授的课程中的研究主题和结果在CMU获得曝光。一个基于LED的推广活动“照明：下一代”将为女工程师协会高中日、匹兹堡公立学校和基督教女青年会TechGyrls项目开发。