Silicon Replacement Generates Little Heat

Professor Walt de Heer leads Georgia Tech research into fabricating electronic devices from epitaxial grapheme, which produces little heat.
Photo by Mali Azima

Move over silicon. There’s a new electronic material in town that generates little heat, and it goes fast.

The material, graphene, which was the focus of the 2010 Nobel Prize in physics, is a fancy name for extremely thin layers of ordinary carbon atoms arranged in a “chicken-wire” lattice. The layers - sometimes just a single atom thick - conduct electricity with virtually no resistance, little heat generation and less power consumption than silicon, say the developers.

By heating silicon carbide, a widely used electronic material, Georgia Tech researchers were able to drive silicon atoms from the surface, leaving just the carbon lattice in thin layers of graphene large enough to grow the kinds of electronic devices familiar to a generation of electronics designers.

With silicon device fabrication approaching its physical limits, many researchers believe graphene can provide a new platform material that would allow the semiconductor industry to continue its march toward ever-smaller and faster electronic devices - progress described in Moore’s Law. Though graphene is not likely to ever replace silicon for everyday electronic applications, it could take over as the material of choice for high performance devices. And graphene ultimately could spawn a new generation of devices designed to take advantage of its unique properties. A new electronics material is needed because silicon is running out of miniaturization room.

“Primarily, we’ve gotten the speed increases from silicon by continually shrinking feature sizes and improving interconnect technology,” says Dennis Hess, director of the National Science Foundation-sponsored Materials Research Science and Engineering Center at Georgia Tech. “We are at the point where in less than 10 years, we won’t be able to shrink feature sizes any farther because of the physics of the device operation. That means we will either have to change the type of device we make, or change the electronic material we use.”

It’s a matter of physics. At the very small size scales needed to create ever more dense device arrays, silicon generates too much resistance to electron flow, creating more heat than can be dissipated and consuming too much power.

Silicon has matured over many generations through constant research and improvement, and many experts agree that it always will be around, useful for low-cost consumer products such as iPods, toasters, personal computers and the like.

But Walt de Heer, a professor in Georgia Tech’s School of Physics who pioneered the development of graphene for high-performance electronics and leads the school’s graphene research, expects graphene to find its niche doing things that could not otherwise be done.

“We’re not trying to do something cheaper or better; we’re going to do things that can’t be done at all with silicon,” he says. “Making electronic devices as small as a molecule, for instance, cannot be done with silicon, but in principle could be done with graphene.”

Much of the world’s graphene research, including work leading to the Nobel Prize, involved the study of exfoliated graphene, which are layers of the material removed from a block of graphite, originally with tape. While agreeing that the exfoliated material has produced useful information about graphene properties, de Heer dismisses it as “a science project” unlikely to have industrial electronics application.

“Electronics companies are not interested in graphene flakes,” he says. “They need industrial graphene, a material that can be scaled up for high-volume manufacturing. Industry is now getting more and more interested in what we are doing.”

“We are not really trying to compete with these other groups,” he says. “We are really trying to create a practical electronic material. To do that, we will have to do many things right, including fabricating a scalable material that can be made as large as a wafer. It will have to be uniform and able to be processed using industrial methods.”