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Computing at the Speed of Light with GaAs Nanowire Lasers - ACT Node

December 2013

Faster, smaller electronics are one step closer with researchers from The Australian National University successfully making the first room temperature lasers from gallium arsenide (GaAs) nanowires. These wires and lasers will lead to faster, lighter computers as light travels faster than electrons allowing data to be processed much faster. Dhruv Saxena, a PhD student at the Department of Electronic Materials Engineering (EME), has just co-authored a paper with Dr Sudha Mokkapati, an ANU-based ARC Super Science Fellow (also at EME), that has been published in NATURE PHOTONICS explaining how to make smaller lasers using GaAs nanowires – solid wires a few billionths of a metre in diameter.

“The lasers in use at the moment often require a lot of processing steps to produce a nice cavity and mirrors in order to emit laser light,” explains Saxena, who went on to say that these older lasers also are much bulkier. These new GaAs wires are ‘grown’ in the lab, using a process called Metal Organic Chemical Vapour Deposition (MOCVD) – one of the tools available at the ACT Node of the ANFF – where a substrate is covered with gold particles that act as catalysts, or ‘seeds’. Gases containing gallium and arsenic are added and the temperature of the substrate is raised up to 750°C. At these temperatures the elements react and nanowires begin to grow.

“It is crystal growth. The substrate provides the direction of the growth, so they grow straight up, standing vertically on the substrate instead of growing in random directions,” says Saxena. This vertical orientation would allow for the fabrication of more compact and densely-packed computer processing chips. Saxena says building computer chips from these wires would still require years of development, but showing that these nanowire lasers can operate at room temperature is an important development that will lead to cheaper, faster and lighter computers.

The research Group GaAs nanowire lasers
The ANU research group: L-R Nian-Jiang, Dr Sudha Mokkapati, Professor Hark Hoe Tan, Dhruv Saxena and Dr Qiang Gao.
(Images supplied by The Australian National University)
An SEM image of the GaAs nanowires growing on the substrate
clearly showing the gold catalyst 'seed' at the top of each nanowire.
Size is ~6 µm high with a diameter of 320 nm.

Professor Chennupati Jagadish, who leads the research, says these lasers are some of the smallest in the world.

“The smaller the lasers the faster we can switch them on and off, so we can send information much faster. “Particularly when you are dealing with computer chips and when you are making electronic devices smaller, the resistance of the metals which are being used to communicate between transistors becomes very large. “This is becoming a real bottle-neck for the speed at which we are able to transfer information between the computer chips and within the computer chips. “That’s where people are looking for optical sources because light can travel much faster.”

Prof. Jagadish says while other nanowires have been developed, they have only been able to operate at lower temperatures.

“Low temperatures mean we won’t be able to use it in day-to-day applications so that’s why making these lasers to work at room temperature is a significant milestone,” he said.

This breakthrough work has received a lot of attention and more articles can be found here:

Nanowires to rev up computers of tomorrow - ABC Science;
Tiny laser breakthrough by ANU researchers shines light on faster computers - ABC News.

And for those you wish to look at the actual NATURE journal publication, you can find it here; (link dependant on appropriate access).