The missing switch new graphene transistors created

Hardly a day goes by without a top-level research group announcingsome kind of graphene-related breakthrough, but this one’s a biggy: Researchers at the University of Erlangen-Nuremberg, Germany have created high-performance monolithic graphene transistors using a simple lithographic etching process. This could be the missing step that finally paves the way to post-silicon electronics.

As you probably know by now, graphene has a long and wonderful list of desirable properties, including being the most conductive material yet discovered. In theory, according to early demos from the likes of IBM and UCLA, graphene transistors should be capable of switching at speeds between 100GHz and a few terahertz. The problem is, graphene doesn’t have a bandgap — an innate ability to switch on and off, depending on the voltage; it isn’t a natural semiconductor, like silicon — and so it is proving very hard to build transistors out of the stuff. Until now!

The process employed by the researchers is quite simple. Basically, by baking silicon carbide — a simple crystal of silicon and carbon, which also happens to be a well-understood semiconductor — the silicon atoms can be driven off from the layer of the crystal, leaving a single layer of graphene. A layer of graphene on its own is useless, though; you need sources, drains, and gates to produce an actual transistor. To do this, a lithographic mask is laid down, and reactive ion etching is used to define each of the transistors. Another key point was the introduction of hydrogen gas during the growth of the middle graphene channel, turning it from contact (source/drain) graphene into gate graphene. Voila: graphene transistors, with the silicon carbide and its delicious bandgap acting as the conducting layer.

Now, unfortunately, because the researchers did their work on a very large scale — each transistor is around 100 micrometers across, or 100,000nm — we don’t really have an accurate measure of just how fast this graphene transistor is. The researchers say that current performance “corresponds well with textbook predictions for the cutoff frequency of a metal-semiconductor field-effect transistor,” but they also point out that very simple changes could increase performance “by a factor of ~30.”

The main thing is that the University of Erlangen-Nuremberg has now provided “the missing switch” that graphene transistors so desperately needed. It will now be up to actual semiconductor manufacturers, such as IBM or Intel, to shrink the process down to a size that can compete — or beat — conventional silicon electronics.