With NSF CAREER Award, Chirag Gupta is using next-gen materials to engineer high performance power semiconductor transistors

But current versions of these power transistors simply can’t handle the increasing demand of emerging next-generation technologies—such as electric transportation and data centers. That’s why Chirag Gupta, an assistant professor of electrical and computer engineering at the University of Wisconsin-Madison, is using a five-year National Science Foundation CAREER award to study transistors made from ultra-wide bandgap semiconductors—materials that could enable our electrified future.

“Our goal is to use this CAREER funding to push these ultra-wide bandgap materials from relatively nascent stage to something that shows their material advantages over incumbent materials,” says Gupta. “We basically want to prove to the world that, yes, these materials are really good and can outperform existing technology.”

For decades, power semiconductor transistors made from cheap and plentiful silicon worked just fine for most power electronics needs. But silicon can’t handle newer applications such as point of load applications, fast chargers, EVs and industrial motors.

A new generation of power semiconductor transistors made from “wide bandgap” materials, including gallium nitride and silicon carbide, has recently hit the market in electric car and fast chargers. The larger the “bandgap” of a semiconductor material, the more voltage and temperature it can handle. And as their fabrication costs decrease, wide bandgap power transistors should quickly find their way into numerous other applications such as computer chips, smart grid components, solar inverters, appliances and other electronic devices.

Gupta and many other electrical engineers, however, anticipate the need for even more powerful transistors in the next few decades as electric motor power and computing needs intensify. That’s why they are working on ways to fabricate transistors from next-generation ultra-wide bandgap materials, including diamond, gallium oxide and aluminum gallium nitride, the material Gupta studies.

“These materials can operate in extreme environments and very high temperatures,” says Gupta. “These are advanced materials compared to the previous generation of transistors, and they can even operate in applications like hypersonic jets, where temperatures can reach up to 800 degrees Celsius (nearly 1,500 degrees Fahrenheit).”

The primary challenge is to create stable, practical and cost-effective transistors from these ultra-wide bandgap materials. Over the course of his project, Gupta plans to conduct several first-of-their-kind studies to fabricate transistors from aluminum gallium nitride and demonstrate their ability to handle voltages significantly higher than silicon and wide bandgap transistors. He and his students will also investigate the transistors’ electric field handling capabilities, reduced resistance, and other unique physical phenomena in the transistors.

At the end of the five-year project, Gupta says he will consider the research a success if he can show a performance advantage for aluminum gallium nitride transistors over commercial transistors. “We want to see this as a serious contender for real-world applications,” he says. “That’s my lab’s mission and vision: to actually transition these technologies to the real world.”

With his prior work experience in the semiconductor industry, Gupta says university-based research like his and that conducted in other labs working on ultra-wide bandgap materials and devices across the United States is crucial to move power electronics forward. “Research like this is too expensive and too risky for industry to do,” he says. “If the technology works and the potential is demonstrated in academia, great, then industry will eventually take over this technology. In case it doesn’t work out, it doesn’t justify the balance sheet for industry. That’s why government support for academic research is crucial: If we don’t do the research, another country will, and then their local industry will benefit instead.”

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