- 25 October 2004 -

Arizona's cooling light

A team led by Yong-Hang Zhang, professor of electrical engineering at Arizona State University, has been awarded a five-year, $1.23m grant from the Department of Defense’s (DoD) Multidisciplinary University Research Initiative (MURI) programme designed to address large multidisciplinary topic areas representing exceptional opportunities for defense and commercial applications.

“From the sheer size of this award, it is clear Dr. Zhang’s work stands to substantially expand our understanding of semiconductor physics, potentially revolutioniding some standard semiconductor processes,” says Dr. Bruce Fette, chief research scientist at General Dynamics and an industrial advisers to the MURI programme.

Zhang, along with collaborator Jose Menendez, professor of physics from ASU’s College of Liberal Arts and Sciences, will research into physics and engineering issues of solid-state refrigeration needed for defense and communications satellites.

Current these use a Stirling cooler technology using a cooling compressor. That can create vibrations hampering many imaging, sensing and navigation components. Zhang says. “There is a tremendous need to have a solid-state cooler, and solid-state means that you don’t have any moving parts.” This cooling equipment is thus expected to last longer, extending satellite longevity and reducing maintenance while in orbit.

The heart of Zhang’sapproach, called electroluminescence upconversion cooling (ELUC), uses semiconductor technology to create the cooling effect. In ELUC, a simple light emitting diode is used to inject electrons into an active region in the device. “The electrons carry the heat from the semiconductor and turn the heat into photons, or photo energy, that leaves the crystal,” Zhang says.

By inputting an electron with a lower energy and having a photon, or particle of light, with higher energy coming out, the cooling effect takes place. While honing the theoretical details, Zhang’s group also will be working to find the right semiconductors, like GaAs and InSb, to optimize the design and deliver a new type of cooling device.

Because the technology is integrated into semiconductors, Zhang envisions being able to adapt this technology to cool computer CPUs and other electronic devices.
It's an approach that's confortable with silico and.could replace the fans and heat sinks that struggle to cool laptop and desktop computers. “I have talked with Intel and IBM, and they are very interested in cooling technology because as CPUs are getting faster, there is more heat coming out of them,” says Zhang.