CAREER: Ultra-wide bandgap AlGaN channel transistors for low loss, high voltage power electronics

Rapid electrification of numerous applications such as transportation, grid and high-power motor drives is going to play a critical role in achieving the goal of a sustainable society. This places an urgent need for efficient utilization of available electric power, considering 80% of the total generated electric power is expected to flow through power electronics by 2030.

The development of innovative and extremely efficient power electronics is critical for incumbent ubiquitous applications as well as new applications such as grid-connected solar inverters, electric cars etc. Furthermore, this will aid in enhancing economic and technical competitiveness of the U.S. At the heart of every power conversion process is a transistor which governs the form-factor, efficiency, and overall system performance.

Therefore, the power semiconductor transistor is a key enabler of extremely energy-efficient power electronics. The emerging electrification needs 1.7 to 10 kV power semiconductor transistors which cannot be served by incumbent solutions. The key objective of this NSF proposal is to demonstrate Ultra-wide band gap transistors up to 10 kV breakdown voltage with ~10x lower on-state resistance compared to the incumbent (SiC) technology and perform a detailed investigation to understand the physical mechanisms which governs transistor operation and reliability.

To achieve these objectives, multiple innovative approaches will be utilized, resulting in numerous first-of-its-kind studies and demonstrations. This research effort will be complemented with efforts for education and workforce development activities as well as broadening participation amongst K-12, pre-college, and college students.

The key objective of this NSF CAREER proposal is to leverage the ultra-wide bandgap material i.e. high composition AlGaN and demonstrate state-of-the-art 10 kV transistors. This project will focus on the following research goals.: 1) First demonstration of Al>0.6Ga<0.4N channel FETs with breakdown voltages >3 kV and up to 10 kV; 2) Achieving near-theoretical electric-field (~10 MV/cm) handling capability in these FETs. 3) Significant reduction of on-resistance by ~10x compared to incumbent SiC technology for 10 kV rated power transistor; 4) First detailed investigation of the electron trapping behavior under stress conditions using photo C-V, time dependent breakdown and hot carrier injection studies in high voltage Al>0.6Ga<0.4N channel transistors; 5) Identification of critical thermal boundary resistances in the Al>0.6Ga<0.4N channel transistor’s epitaxial structure and strategies to minimize them.

Additionally, a competitive STEM workforce will be trained through curated wide band gap semiconductor short courses for industry professionals and also by working with industry and local technical colleges to offer a hands-on internship program to meet rising technician needs. Furthermore, efforts will be made to enhance education by training a high school teacher in wide band gap semiconductors and developing a hands-on activity to be integrated in advanced physics curriculum at high school level.

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.