Graphene Ready To Conquer The Terahertz Terrain

Jan. 17, 2012
Researchers have demonstrated a subharmonic graphene FET mixer at microwave frequencies.

Mikael Fogelström and Sergey Kubatkin are two of Chalmers’ researchers investigating the supermaterial graphene. The cryostat shown is used to cool graphene samples to 1/100th of a degree above absolute zero.

In a major breakthrough, researchers at Chalmers University of Technology in Sweden demonstrated a subharmonic graphene FET mixer at microwave frequencies. The mixer is regarded as a key electronic design element, because it can combine two or more electronic signals into one or two composite output signals. Its potential will ultimately be realised in future applications requiring terahertz frequencies.

The speed of the electrons in silicon has reached its limit, at least that’s the prevailing opinion. However, estimates show that electrons become 100 times quicker with graphene.

Furthering the case for graphene is that it’s a transparent conductor with the ability to combine electrical and optical functionalities. Graphene can switch between hole or electron carrier transport via field effect, which translates into rather significant potential for future RF IC applications.

Chalmers’ researchers managed to build a G-FET subharmonic resistive mixer using only one transistor. As a result, it requires no extra feeding circuits, creating a more compact mixer circuit. In turn, it occupies less wafer area when constructed.

Beyond size reduction, the G-FET offers the potential to reach high frequencies thanks to graphene’s high-speed characteristics, and the fact that a subharmonic mixer only requires half the local-oscillator (LO) frequency of a fundamental mixer. The latter property is particularly attractive at high frequencies (terahertz), due to a lack of sources providing sufficient LO power. Moreover, the G-FET can be integrated with silicon technology (e.g., it’s CMOS-compatible).

The coordinated development of graphene-related technology is funded by the European Commission in a 10-year, 1000 million plan to develop a FET flagship product. The vision of this ambitious research initiative is to produce a breakthrough for technological innovation and economic exploitation based on graphene and related two-dimensional materials.

The graphene flagship project already includes over 130 research groups, representing 80 academic and industrial partners in 21 European countries. It’s headed by a consortium of nine partners who pioneered graphene research, innovation, and networking activities. Coordinated by Chalmers University of Technology in Sweden, it includes the Universities of Manchester, Lancaster, and Cambridge in the U.K., the Catalan Institute of Nanotechnology in Spain, the Italian National Research Council, the European Science Foundation, AMO GmbH in Germany, and the Nokia Corporation.

All of this activity follows trailblazing graphene-related experiments in 2004 by European scientists Andre Geim and Konstantin Novoselov, who were awarded the 2010 Nobel Prize in Physics. Their work sparked a scientific explosion, best illustrated by the growth of patent applications related to graphene.

The U.S., Japan, Korea, Singapore, and other countries are investing huge amounts of human resources and capital into graphene research and applications. Korean chipmaker Samsung predicts that the first graphene-based devices will appear in 2014.

About the Author

Paul Whytock

Paul Whytock has reported on the electronics industry for over twenty years. He qualified in electrical, mechanical, and production engineering at the Ford Motor Companys European Engineering School. He also worked as a design engineer at Ford locations in England, Germany, Holland, and Belgium. Whytock joined Electronics Times Newspaper as Deputy Editor in 1982 and has since worked on various international electronics publications as Editor-in-Chief.

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