ASCENT: Enabling efficient high power grid applications by high voltage rating ultrawidebandgap transistors

This project aims to both understand the science and develop engineering of an emerging ultra-widebandgap semiconductor, gallium oxide, for the next generation high voltage, high current power electronics. Power electronics plays an essential role in several innovative technologies including integration of renewables to grid, electric cars, planes, and ships to name a few. The multidisciplinary team addresses several challenges spanning from the synthesis of low defect density materials to applications and benchmarking of device prototypes in high power converters. An important challenge in high power applications is the ability to manage heat dissipation during the device operation. This project addresses this challenge by integrating gallium oxide with a high thermal conductivity material which can efficiently dissipate heat. Additionally, innovative device designs and circuit topologies will be developed for high voltage, high power and low loss operation. Success in the program would enable power device and circuit technologies beyond the state-of-the-art technologies. The new technology would foster innovation in power electronics market. The fundamental study aspects of the project would increase the understanding of the electronic properties of ultra-widebandgap semiconductors which have applications beyond power electronics. The education and training of the diverse students working on the project would enhance their technical skills in semiconductor manufacturing. Domestic semiconductor manufacturing is currently a national priority for US economic leadership and national security. Educational outreach activities will be integrated with research tasks. The goal of the outreach efforts is to inculcate interest of middle and high school students to science and engineering fields. Beta-gallium oxide (Ga2O3) has achieved robust maturity with low background doping densities, excellent doping control and electron mobilities reaching theoretically predicted values. The large predicted and experimentally demonstrated electric field strengths and good electron mobility makes it an attractive semiconductor for high voltage (> 10 kV) rating power devices. Such high voltage ratings can be achieved in thin drift layers that can be grown with low defect densities and high uniformity by metal organic chemical vapor deposition (MOCVD). The project leverages the experimental demonstration of in-situ Mg doped current blocking layers grown by MOCVD. The team has also demonstrated integration of gallium oxide onto high thermal conductivity substrates. The scientific objectives of this project are (i) developing and optimizing in-situ Mg doped current blocking and thick Ga2O3 drift layers with low controllable doping for high voltage and high power operation; (ii) design, fabrication, and measurement of high power MOSFETs with high breakdown blocking capability; (iii) heterogeneous integration of the power devices onto high thermal conductivity substrates for thermal management and (iv) investigation of switching losses and paralleling techniques, as well as benchmarking of practical circuits using the developed power devices. If successful, the proposed innovative device will enable efficient high-power switches with beyond 10 kV voltage ratings thus drastically reducing the cost and increasing the efficiency of high-power circuits. These technologies can accelerate the integration of renewables to the grid and lead to truly smart grid operation. The integrated education plan aims to educate and motivate young students to pursue STEM studies and careers by direct participation in the proposed research activities. The research opportunity given to undergraduate and graduate students will help build the skills of the future semiconductor workforce for domestic manufacturing and maintain the economic competitiveness of the US. 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.