Record-setting 2.75 gigahertz LED designed for fast, energy-efficient data centers

A collaboration between the University of Illinois Urbana-Champaign’s Grainger College of Engineering and the University of Notre Dame has broken the world record for optical switching speed in quantum well LEDs. The gallium nitride micro-LED device has an optical modulation bandwidth of 2.75 gigahertz while consuming just 25 milliwatts of power. Its design was optimized to bring newfound speed and efficiency to communication links in data centers.

As the team of researchers reports in IEEE Electron Device Letters, this achievement is the result of an extensive program of theoretical modeling and empirical testing, providing a roadmap to scaling down LED devices for optical communications. For the record-breaking device, the design was optimized to a size of 5 micrometers. The team hopes that their design will prove to be a vast improvement in speed and efficiency over conventional wire interconnects and even laser-based optical links for short-range communication.

“Ninety percent of communications in data centers is short range, meaning less than 10 meters,” said Illinois Grainger Engineering graduate student Abdelghany Abouelnagga, the study’s lead author. “It is standard to use lasers for the kind of high-frequency communications needed in this context, but lasers are power hogs. If we want to manage energy use in data centers, we need to consider lower-power optical communications such as LEDs, and we show exactly how to do so.”

This study was conducted by the research groups of Illinois Grainger Engineering electrical and computer engineering professors Can Bayram, Peter Dragic and Milton Feng; and Notre Dame electrical engineering professor Patrick Fay.

To increase the speed with which data centers operate, it has been necessary to use optical communication links that transmit information using light pulses. Unlike copper wires, optical links can transmit at very high rates, or frequencies, without experiencing significant loss. It is necessary to use a tightly controlled light source to achieve high frequencies without sacrificing accuracy.

Until now, that has meant using lasers, but they require large amounts of power and generate large amounts of heat. The alternative is to use another tightly controlled light source such as LEDs. To create a device that is not only fast but optimized for use in data centers, the researchers systematically studied how the optical modulation bandwidth — a measure of how fast the micro-LED can switch on and off before the light loses brightness — and power consumption vary with device size.

“We systematically shrunk our micro-LEDs down from 100 micrometers to 2 micrometers in diameter, a level of deep scaling that has never been done before,” Abouelnagga said. “We found that, contrary to popular belief, smaller is not always better. Our work gives a development roadmap to systematically study the tradeoffs between size, bandwidth and power consumption, which shows that the best device is actually the 5-micrometer one.”

To fabricate their optimized micro-LED devices, the researchers needed to have a precise understanding of the material imperfections leading to so-called parasitic effects in device performance. Abouelnagga recalls that it was necessary to model the materials and electrical properties in detail beforehand to ensure an optimal design.

The device’s performance is a record for quantum well LEDs, the industry standard design. Certain nonstandard LED designs can operate at higher frequencies, but such designs create unstable, low-intensity light. The researchers believe their 5-micrometer quantum well design is much better suited to data center usage not only for its optical power and bandwidth, but for its extraordinarily low energy consumption and material platform scalability.

“To put the speed and power efficiency in perspective, our micro-LED responds to electrical signals on a gigahertz scale, comparable to computer processors, but consumes just 25 milliwatts of electrical power,” Abouelnagga said. “Of course, processors and optical transmitters perform different functions, but the comparison illustrates how fast this tiny light source can respond with a small power budget. Its 5-micrometer diameter also opens the possibility of arranging many emitters into compact, two-dimensional arrays with each carrying a separate stream of data.”

Zetai Liu and Jonathan Wright also contributed to this study.

The article, “Scaling of GaN Micro-LEDs with a 2.75 GHz Bandwidth for High-Speed Optical Links,” is available online. DOI: 10.1109/LED.2026.3745737

Illinois Grainger Engineering Affiliations

Can Bayram is an Illinois Grainger Engineering professor of electrical and computer engineering in the Department of Electrical and Computer Engineering. He is a resident faculty member in the Holonyak Micro and Nanotechnology Laboratory. He holds an Intel Alumni Endowed Faculty Scholar appointment.

Peter Dragic is an Illinois Grainger Engineering associate professor of electrical and computer engineering in the Department of Electrical and Computer Engineering. He is a resident faculty member in the Holonyak Micro and Nanotechnology Laboratory.

Milton Feng is an Illinois Grainger Engineering Professor Emeritus of electrical and computer engineering in the Department of Electrical and Computer Engineering. He is affiliated with the Coordinated Science Laboratory and the Holonyak Micro and Nanotechnology Laboratory. He holds a Nick Holonyak, Jr. Endowed Chair Emeritus appointment.