Nanowires on silicon get three times faster

The integration of semiconductor nanowires with conventional silicon electronics has overcome a major hurdle thanks to researchers at the London Centre for Nanotechnology and UCL’s Department of Electrical Engineering.

Writing in a recent issue of Nano Letters, Marion Sourribes, Paul Warburton and their collaborators have measured the electronic properties of indium arsenide nanowires which were grown directly on silicon wafers. They showed that by adding small amounts of antimony to the recipe, electrons travel three times faster than in pure indium arsenide nanowires.

One of the microelectronics industry’s biggest headaches right now is that the cost of manufacturing ever smaller silicon transistors is becoming prohibitively expensive – with the cost of setting up a single silicon factory now ten billion dollars and rising. Since smaller transistors means faster transistors (which in turn means more computing power), researchers are trying to identify new cost-effective technologies which could in the long term replace silicon transistors. Indium arsenide nanowires are one such possible technology.

“Indium arsenide nanowires have excellent electronic properties” commented Dr Warburton, “but previously they have been grown on very expensive carrier substrates.”

Previous attempts to grow them on silicon substrates resulted in nanowires containing a high density of defects, resulting in poor electronic properties. The UCL team studied what happened when small amounts of the element antimony were added to the indium arsenide nanowires as they were being grown.

“Structural characterisation performed by electron microscopy showed that the defect density had greatly reduced – and that correlated with a considerable improvement in the electronic properties” said Ms Sourribes.

In fact the mobility of the electrons (which determines how fast a transistor can switch on and off) went up by a factor of three by comparison with nanowires not containing antimony.

“We can now start to think about real applications exploiting both the unique properties of the nanowires and the well-established processing power of silicon” continued Dr Warburton.

Possibilities being considered by the UCL team include thermoelectric nano-generators, detectors of infra-red light and electronically-tuneable gas sensors.

Journal link: Mobility Enhancement by Sb-mediated Minimisation of Stacking Fault Density in InAs Nanowires Grown on Silicon. http://pubs.acs.org/doi/pdf/10.1021/nl5001554

Figure: (left) Electron microscope image of nanowires grown on a silicon substrate (Sourribes et al.). (right) Electron microscope image of a nanowire connected by two metallic contacts (Sourribes et al., Nanotechnology, 24, 045703, 2013).

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