CAREER: Ultrawide Bandgap Aluminum Nitride FETs for Power Electronics

电力电子日益成为交通电气化、可再生能源、电网现代化和减少碳排放的关键推动因素，以实现绿色、可持续的经济。最先进的硅功率器件正在接近硅材料的极限，这促使人们为下一代电力电子探索新的半导体。超宽带隙(UWBG)半导体具有独特的材料特性，可用于未来的电力电子产品，其性能有望远远超过现有的硅以及成熟的氮化镓和碳化硅电力技术。氮化铝(AlN)是超宽带半导体中带隙最大、临界电场最大的半导体材料，具有良好的导热性能，使电力电子具有更高的效率、更高的电压、更高的频率和更高的工作温度。然而，目前的AlN功率器件的性能远远落后于AlN材料的限制，这是由于对AlN外延、表面、接触和器件的基础了解不足。该项目旨在通过创新的集成材料和器件工程，显著推动用于高性能电力电子的UWBG AlN基场效应晶体管(FET)的开发。AlN功率FET的关键材料和器件障碍将被解决，该项目将导致对AlN及其外延科学、表面、触点和功率器件的新的基本见解。这项研究有望充分释放UWBG AlN在高效、高压、快速、紧凑和坚固耐用的电力电子方面的潜力，并对其他UWBG半导体的基础研究和器件开发具有变革性。UWBG AlN电力技术的成功成果可以提高能源效率和安全性，减少化石燃料消耗，提高电网的弹性和效率，增强电动汽车和可再生能源的普及率，并为实现碳中性和净零碳目标做出重大贡献。此外，该项目将为本科生、研究生和K-12年级的学生提供各种关于功率半导体的教育机会，并增强STEM领域的学生多样性，包括指导本科生的研究，开发新的半导体课程，为K-12学生组织外展和实习计划，扩大未被充分代表的群体在STEM中的参与，以及与半导体行业合作进行劳动力培训。该项目的总体目标是通过整体材料和器件工程开发高性能的UWBG AlN功率FET，用于下一代高效、高压、高温电力电子产品。提出了五个研究方向，以解决性能接近AlN极限的AlN功率FET的关键材料和器件障碍。AlN外延科学与工程将对金属有机化学气相沉积(MOCVD)AlN同质外延的生长动力学和掺杂机制有一个基本的了解，并阐明同质外延AlN中的缺陷、掺杂和载流子输运。推力2中的氮化铝表面科学和工程将极大地丰富氮化铝在不同晶体取向上的表面科学和知识，利用综合的材料和电学表征，并开发有效的表面工程来减轻不利的表面效应。推力3中的AlN接触研究和优化将通过新的再生长和加工技术增强和优化AlN FET中必不可少的AlN肖特基和欧姆接触。推力4中的AlN功率器件工程将实施创新的电场管理方法，以防止器件过早失效，并借助其他推力的器件建模和材料创新开发常断的AlN功率FET。Struts 5将实现单片集成的AlN电力电子产品，具有功率FET、驱动器和控制电路，具有更高的效率、更高的功率密度、更快的开关、更小的外形因数和更高的稳健性，这是同类产品中的第一项。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Power electronics are increasingly becoming key enablers for transportation electrification, renewable energy, grid modernization, and carbon emission reduction for a green, sustainable economy. The state-of-the-art silicon power devices are approaching silicon material limits, which urges the exploration of new semiconductors for next-generation power electronics. Ultrawide bandgap (UWBG) semiconductors possess unique material properties for future power electronics that promise far superior performance beyond the incumbent silicon and maturing gallium nitride and silicon carbide power technologies. Aluminum nitride (AlN) exhibits the largest bandgap and critical electric field in the UWBG semiconductor family with excellent thermal conductivity, which can enable power electronics with higher efficiency, higher voltage, high frequency, and higher operation temperature. However, the performance of current AlN power devices lags far behind AlN material limits due to poor fundamental understanding of AlN epitaxy, surfaces, contacts, and devices. This project aims to significantly advance the development of UWBG AlN-based field-effect transistors (FETs) for high-performance power electronics through innovative integrated material and device engineering. Critical material and device obstacles for AlN power FETs will be tackled, and the project will lead to new fundamental insights into AlN and its epitaxial science, surface, contacts, and power devices. This research is promising to unlock the full potential of UWBG AlN for high-efficiency, high-voltage, fast, compact, and robust power electronics and transformative for other UWBG semiconductors’ fundamental research and device development. The successful outcome of the UWBG AlN power technology can increase energy efficiency and security, reduce fossil fuel consumption, improve resiliency and efficiency of the electric grid, enhance penetration of electric vehicles and renewables, and significantly contribute to carbon neutral and net-zero carbon goals. In addition, this project will offer various education opportunities for undergraduate, graduate, and K-12 students on power semiconductors and enhance student diversity in STEM fields, including mentoring undergraduates in research, developing new semiconductor curriculum, organizing outreach and intern programs for K-12 students, broadening the participation of underrepresented groups in STEM, and collaborating with semiconductor industry for workforce training.The overarching goal of this project is to develop high-performance UWBG AlN power FETs through holistic material and device engineering for next-generation high-efficiency, high-voltage, high-temperature power electronics. Five research thrusts are proposed to address crucial material and device impediments toward AlN power FETs with performance close to AlN limits. AlN epitaxy science and engineering in Thrust 1 will obtain a fundamental understanding of growth dynamics and doping mechanisms of AlN homoepitaxy via metalorganic chemical vapor deposition (MOCVD) and shed light on defects, doping, and carrier transport in homoepitaxial AlN. AlN surface science and engineering in Thrust 2 will significantly enrich the surface science and knowledge of AlN on different crystal orientations using comprehensive material and electrical characterizations and develop effective surface engineering to mitigate adverse surface effects. AlN contact study and optimization in Thrust 3 will enhance and optimize AlN Schottky and ohmic contacts essential in AlN FETs via novel regrowth and processing technologies. AlN power device engineering in Thrust 4 will implement innovative electric field management approaches to prevent premature device failure and develop normally-off AlN power FETs with the aid of device modeling and material innovations from other thrusts. Thrust 5 will realize monolithically integrated AlN power electronics with power FETs, drivers, and control circuits for higher efficiency, higher power density, faster switching, smaller form factor, and higher robustness, which is the first of its kind.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.