Single QD nanowire photodetectors

In another step toward quantum computing, researchers have made a photodetector based on a single nanowire, in which the active element is a single quantum dot (QD) with a volume of only 7000 nm³.

The nanowire, which was made of indium phosphide, was grown using standard epitaxial techniques; sandwiching a thin segment in between with a lower bandgap enabled the researchers to obtain the quantum dot. They used electron beam lithography to contact a single nanowire to create the device.

The photocurrent from the nanowire detector: The yellow spot represents the region where current is generated under illumination, the electrical contacts are indicated in blue, and the nanowire is indicated in green. Courtesy of Val Zwiller, Kavli Institute of Nanoscience at Delft University of Technology.

Quantum dots have discrete energy levels, so the device will detect light in resonance only with the energy levels of the quantum dot. It functions as a highly localized light detector and, because its dimensions are far below the wavelength of light, it can detect light with very high spatial resolution, according to the research team at the Kavli Institute of Nanoscience at Delft University of Technology.

The article appears in the journal Applied Physics Letters, Vol. 97, p. 113108 (2010).