Nanowire light detectors around the corner

Published 26 April 2007

The geometry of nanowires — with so much surface area relative to volume — makes them inherently good at trapping holes, and when holes are trapped, the time it takes electrons and holes to recombine increases

Researchers at the University of California-San Diego are bringing nearer the day of nanowire light detectors — with single-photon sensitivity to boot. Nanowires are crystalline fibers about one-thousandth the width of a human hair, and their properties will likely allow new photodetector architectures for sensing, imaging, memory storage, intrachip optical communications, and other nanoscale applications, according to a new study in an upcoming issue of the journal Nano Letters. The UCSD engineers show 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,” says 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 zip along the nanowire and generate electric current under an applied electric field -