CAREER: Ultrawide Bandgap Aluminum Nitride FETs for Power Electronics

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.