Unlike any other in the world, the new Wisconsin Center for Semiconductor Thermal Photonics at the University of Wisconsin-Madison will combine research in photonics, thermal science, and quantum science to understand how semiconductors could be used to control the flow of heat. That understanding will be beneficial as researchers seek to develop new types of power generation, energy conversion, refrigeration, advanced sensing and other next-generation applications.
“If you asked somebody 20 years ago what semiconductors are good for, they would probably tell you electronic computing elements like CPUs or GPUs,” says Mikhail Kats, an associate professor of electrical and computer engineering at UW-Madison. “Somebody a bit more forward-looking might have added that they’re also becoming important for optical components. In the future, they will also be used to control the flow of heat and light, and in various emerging quantum technologies.”
Kats is among six co-principal investigators in the center, which brings together faculty from multiple engineering and physics backgrounds. The researchers say the confluence of several events makes this an ideal time to launch the center.
When quantum mechanics was developed more than a century ago, thermal radiation was one of the first phenomena explained by the then-radical new theory. Now, there is big resurgence in research in the manipulation and applications of thermal radiation, with researchers like Mechanical Engineering Assistant Professor Dakotah Thompson, Electrical and Computer Engineering Associate Professor Zongfu Yu and Assistant Professor Eric Tervo using new techniques and tools to focus on fundamental questions and new technologies. For example, Tervo is developing ways to actively control the flow of heat by manipulating thermal radiation in nanostructured materials.
Additionally, the CHIPS and Science Act, which passed in summer 2022 and aims to bolster U.S. semiconductor manufacturing and research, is opening up new funding sources and multi-institution research collaborations. UW-Madison has a strong convergence of people working in semiconductors, optics, and thermal and quantum research, making it an ideal place to investigate this less-trodden side of semiconductor science and technology.
“The continuation of Moore’s Law faces substantial challenges because it is becoming difficult to pack more silicon transistors onto chips. Semiconductor researchers need to go in other directions and bring in new materials,” says Tervo. “This is beneficial to applications other than computing, because alternative materials will open up opportunities in fields like power conversion, photonics, and sensing. So we have a mutually beneficial situation where interest in semiconductor science and onshoring a semiconductor workforce will have beneficial effects in a whole variety of fields.”
The center, which recently received two years of seed funding from UW-Madison’s Research Forward initiative, will have three initial thrusts. In the first, the team plans to delve into the fundamentals of thermal radiation, which is typically broadband with no preference in direction, like the light from an incandescent light bulb. Center researchers will explore ways of imparting directionality to thermal radiation, and to create thermal devices that operate at specific wavelengths. “There are many optical frequencies where lasers and LEDs cannot operate efficiently for reasons that are not limiting to thermal radiation” says co-PI Victor Brar, an assistant professor in physics and affiliate of materials science and engineering. “We want to explore the extent to which thermal devices can fill those gaps.”
The second thrust is focused on developing new types of tools to enable more precise research, including new types of spectroscopy and all-optical quantum thermometry. “The first lecture in any introductory quantum class I teach covers Planck’s law of thermal radiation as one of the founding principles for developing quantum mechanics,” says ECE Assistant Professor Jennifer Choy. “Now, our center can explore further intersections between thermal and quantum technologies and enable new measurement techniques.”
In the third thrust, the team will develop thermal photonic devices. For instance, Tervo is developing ways to convert thermal radiation into electricity with semiconductor devices similar to the way that solar cells convert sunlight into electricity. On the flip side, this type of precise heat management could also lead to new types of refrigeration that requires no moving parts or fluids. The possibilities are vast: In the future, the team envisions semiconductor devices enabling technologies like heaters that track individuals around a room, directing warmth on them like a personal sunbeam instead of heating the entire area.
The six investigators will be collaborating on a paper that lays out a five-year roadmap for semiconductor thermal photonics, which they say will help establish UW-Madison as leader in the emerging space.
“The definition of semiconductors as a discipline is going to expand quite dramatically,” says Kats. “And that’s the point. Ours is a semiconductor center that isn’t explicitly about microelectronics or computing. It is about expanding the role of these materials and the fabrication techniques and science involved to encompass a much bigger place in society.”
Kats is Jack St. Clair Kilby Associate Professor, Antoine-Bascom Associate Professor, and H.I. Romnes Faculty Fellow. Yu is Jack St. Clair Kilby Associate Professor and H.I. Romnes Faculty Fellow.
Featured image caption: Assistant Professors Eric Tervo (left), Jennifer Choy (center) and Dakotah Thompson (right) are bringing expertise in quantum mechanics, thermal emissions and measurement techniques to the new Wisconsin Center for Semiconductor Thermal Photonics. Credit: Joel Hallberg.