Little Impurities Make Nanolasers Shine

A silicon wafer on which nanostructures are grown (Source: ANU)

A silicon wafer on which nanostructures are grown (Source: ANU)

Scientists at The Austra­lian National University ANU have improved the performance of tiny lasers by adding impurities, in a discovery which will be central to the develop­ment of low-cost biomedical sensors, quantum computing, and a faster internet. Researcher Tim Burgess added atoms of zinc to lasers one hundredth the diameter of a human hair and made of gallium arsenide – a material used extensively in smart­phones and other electronic devices. The impurities led to a 100 times improve­ment in the amount of light from the lasers.

“Normally you wouldn’t even bother looking for light from nanocrystals of gallium arsenide. We were initially adding zinc simply to improve the electrical conduc­tivity,” said Burgess, a PhD student in the ANU Research School of Physics and Engineering. “It was only when I happened to check for light emission that I realised we were onto something.”

Gallium arsenide is a common material used in smart­phones, photovoltaic cells, lasers and light-emitting diodes, but is challenging to work with at the nanoscale as the material requires a surface coating before it will produce light. Previous ANU studies have shown how to fabricate suitable coatings. The new result complements these successes by increasing the amount of light generated inside the nano­structure, said research group leader Chennupati Jagadish, from the ANU Research School of Physics Sciences. “It is an exciting discovery and opens up oppor­tunities to study other nano­structures with enhanced light emission efficiency so that we can shrink the size of the lasers further,” he said.

Tim Burgess said that the addition of the impurity to gallium arsenide, a process called doping, improved not only the light emission. “The doped gallium arsenide has a very short carrier lifetime of only a few pico­seconds, which meant it would be well suited to use in high speed electronics components. The doping has really has given these nanolasers a per­formance edge.” (Source: ANU)

Reference: T. Burgess et al.: Doping-enhanced radiative efficiency enables lasing in unpassivated GaAs nanowires, Nat. Comm., online 17 June 2016; DOI: 10.1038/ncomms11927

Link: Dept. of Electronic Materials Engineering, The Australian National University, Canberra, Australia

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