Researchers get around bad gap problem with graphene by using negative differential resistance
PostedAugust 23, 2013
Researchers get around bad gap problem with graphene by using negative differential resistance Experimentally observed negative differential resistance characteristics in graphene devices. (a) SEM of top-view SEM of a typical dual-gate graphene device. Gold color is the source/drain, pink color is the top gate and the blue color underneath is graphene flake. The gate and graphene channel is separated by a two-layer of AlOx and HfO2 oxide stack. The scale bar is 1μm. (b) The transfer characteristics of BLG device under different back-gate voltage. The increased resistance at large back-gate voltage indicated band gap opening by perpendicular electric field. The inset shows the Dirac point shift as the back-gate voltage changes. Credit: arXiv:1308.2931 [cond-mat.mes-hall]
A team of researchers at the University of California has come up with a way to use graphene in a transistor without sacrificing speed. In a paper they’ve uploaded to the preprint server arXiv, the team describes how they took advantage of a property of graphene known as negative differential resistance to coax transistor-like properties out of graphene without causing it to behave as a semiconductor.
As most everyone knows, using silicon as the basis for building transistors is reaching its logical conclusion—basic physics dictates that transistors based on it can only be made so small. Thus, efforts have been underway for several years to find a replacement material. One of the leading candidates, of course, is graphene—it has a variety of properties that would make it ideal, the best of which is the incredible speed in which electrons can move through it. Unfortunately, graphene is not a semiconducting material—it has no bad gap. That makes it useless as material for use in a transistor, which by its very nature must have a component that turns on and off. Graphene stays on all the time.
Researchers have spent a lot of time, money and effort trying to force graphene to behave like a semiconductor, but most efforts have either failed completely, or resulted in a slowdown of the movement of electrons—defeating the whole point of using grahene in the first now. Now, however, it appears the team at UC has found a way to use graphene in a transistor, without forcing it to have a band gap.