Record-setting gallium nitride transistor operates at 800 degrees Celsius

Silicon has been pushed to its limit. Its natural abundance and unique combination of electronic, mechanical and thermal properties have made it the pillar of the digital computing revolution. But, as we push digital technology into extreme environments such as outer space and geothermal vents, silicon cannot hold up in the high temperatures.

One alternative is gallium nitride (GaN), a semiconductor already being used to make high-speed devices that also have a wide enough bandgap to support high-temperature operation. The difficulty has been engineering the transistor structure to fully exploit the thermal stability offered by the GaN materials. Recent work led by Rongming Chu, professor of electrical and computer engineering in The Grainger College of Engineering at the University of Illinois Urbana-Champaign, has demonstrated how GaN-based devices can operate at markedly higher temperatures.

Chu’s research group reported a GaN transistor design that operated at 800 degrees Celsius with an on/off current ratio of 770, representing the highest-performing GaN device that has been reported at this temperature. This result indicates that such devices hold great promise for applications where both speed and heat tolerance are important. The study was published in IEEE Electron Device Letters, where it was featured on the September 2025 cover.

“Transistor devices – the building blocks underpinning electronics – operate by switching between conducting and nonconducting states,” Chu explained. “When these devices go to higher temperatures, the electrons in the device can draw on the thermal energy to make the device conducting even if you wanted to switch it off. Our GaN transistor design makes key progress towards high-temperature operation stability by redesigning materials, device structures and device processes, resulting a very clean on/off signal under extreme conditions.”

The GaN transistor developed by the Chu group belongs to a class of devices called high-electron-mobility transistors (HEMTs). They incorporate a heterojunction between two materials to engineer a solid-state phenomenon known as a “two-dimensional electron gas,” in which electrons are confined within a very thin sheet at the boundary between the two materials. Electrons in the gas move very fast, offering high transistor speed. They are also easily controlled by the gate electrode, making the device scalable to smaller dimensions and even higher speed.

“Speed is a key advantage of GaN as a basis for semiconductor technology,” Chu said. “There’s another material, silicon carbide, that gets attention for its thermal tolerance properties, but the devices demonstrated so far are much slower. So, even though GaN is the least thermally stable of the two, I believe that this is the material worth pursuing. And our new design shows that devices can be engineered to operate at 800 degrees Celsius.”

Looking ahead, Chu believes that the design can be made even better by managing leakage current from the gate and by scaling the device for even higher on-current and higher speed. These improvements would enable large-scale integrated circuits for high-performance electronics at high temperatures.

“At the time of writing our article, the device set a record,” Chu said. “We’ve already broken it in work that was featured in IEEE Spectrum. There’s so much room to improve thermal stability and to explore potential applications.”

Ajay Visvkarma, Juan Jimenez Gaona, Chan-We Chiu, Yixin Xiong, Yi-Shuo Hang, Rian Guan, Nathan Banner and Suzanne Mohney also contributed to this study.

The researchers’ article, “p-GaN Gated HEMT With 770 ION/IOFF Ratio Operating at 800 °C,” is available online. DOI: 10.1109/LED.2025.3585816

Support was provided by the Defense Advanced Research Project Agency and the National Science Foundation.

Illinois Grainger Engineering Affiliations

Rongming Chu is an Illinois Grainger Engineering professor of electrical and computer engineering in the Department of Electrical and Computer Engineering. He is affiliated with the Holonyak Micro and Nanotechnology Laboratory.