Nanoscale light detection

The geometry of semiconducting nanowires makes them uniquely suited for light detection, according to a new

study that highlights the possibility of nanowire light detectors with single-photon sensitivity.

Nanowires are crystalline fibres and their inherent properties are expected to enable new photodetector architectures for sensing, imaging, memory storage, intrachip optical communications and other nanoscale applications, according to a new study in an issue of the journal Nano Letters. The UCSD engineers illustrated why the large surface areas, small volumes and short lengths of nanowires make them extremely sensitive photodetectors, much more sensitive than larger photodetectors made from the same materials.

‘These results are encouraging and suggest a bright future for nanowire photodetectors, including single-photon detectors, built from nanowire structures,’ said Deli Wang, an electrical and computer engineering professor from the UCSD Jacobs School of Engineering and corresponding author on the Nano Letters paper.

For a nanowire to serve as a photodetector, photons of light with sufficient energy must hit the nanowire in such a way that electrons are split from their positively charged holes. Electrons must remain free from their holes long enough to move along the nanowire and generate electric current under an applied electric field, a sign that light has been detected.