VerticalTransistorM 2012

Graphene Transistor Hurdle Cleared

A major hurdle in the race to manufacture a graphene computer chip has been cleared by scientists at the University of Manchester. The team of researchers lead by the Nobel Laureates Andre Geim and Konstantin Novoselov, have happily announced that the problem of graphene’s near super-conductivity has now been solved. The research finding is set to reignite the race for a graphene transistor and the race is now on to see which team will be the first to make the breakthrough device that will make graphene the new silicon.

Using graphene instead of silicon in the manufacture of transistors has already been accomplished by some of the world’s leading chip manufacturing  companies IBM, Samsung, Texas Instruments and Intel have all been working with graphene to construct a new transistor and individual transistors with very high frequencies (up to 300 GHz) have already been demonstrated by several groups worldwide. However, a single problem remained, the transistors leaked too much current which in turn caused the chips to melt within fractions of a second.

Solving the problem of graphene’s conductivity has been on the agenda since 2004, and only now has the problem been solved; the irony is that the great leap forward required a simple piece of lateral thinking. The University of Manchester scientists worked on using graphene not laterally (in plane) – as all the previous studies did – but in the vertical direction. They used graphene as tunnelling diode and produced a device that encourages electrons to tunnel through a dielectric into another metal.

They then exploited a truly unique feature of graphene – that an external voltage can strongly change the energy of tunnelling electrons. As a result they got a new type of a device – vertical field-effect tunnelling transistor in which graphene is a critical ingredient.

Commenting on the finding Dr Leonid Ponomarenko, who spearheaded the experimental effort, said:

We have proved a conceptually new approach to graphene electronics.  Our transistors already work pretty well. I believe they can be improved much further, scaled down to nanometre sizes and work at sub-THz frequencies.

The new device was made from a layer cake of graphene combined with atomic planes of boron nitride and molybdenum disulfide. The nanoscale superstructure is entirely artificial and introduces a new concept for later use. The atomic-scale assembly offers many new degrees of functionality, without some of which the tunnelling transistor would be impossible.

“The demonstrated transistor is important but the concept of atomic layer assembly is probably even more important,” explains Professor Geim.

Professor Novoselov added:  “Tunnelling transistor is just one example of the inexhaustible collection of layered structures and novel devices which can now be created by such assembly… It really offers endless opportunities both for fundamental physics and for applications. Other possible examples include light emission diodes, photovoltaic devices, and so on.”

The paper, Field-effect tunneling transistor based on vertical graphene heterostructures, by L. Britnel1, R. Gorbache2, R. Jalil, B. Bell2, F. Schedin, A. Mishchenko, T. Georgiou, M. Katsnelson, L. Eaves, S. Morozov, N. Peres, J. Leist, A. Geim, K. Novoselov, and L. Ponomarenko, embargoed by Science until 7pm GMT Thursday 2nd February 2012,  is available from the University of Manchester Press Office.

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