Optically Active Quantum Dots Embedded in Nanowires

Daniel S. Burgess

Investigators at the Swiss Federal Institute of Technology in Zurich have reported the fabrication of quantum dots in nanowires that display a level of brightness an order of magnitude higher than self-assembled InAs dots. They suggest that the work may have an impact on the development of so-called quantum dot molecules for quantum information processing as well as of devices that integrate electronics and optics, particularly because the structures can be grown on silicon.

The researchers produced the structures by low-pressure metallorganic vapor phase epitaxy, embedding 15-nm alloys of GaAsP in 200- to 500-nm-long segments of GaAsP with a higher bandgap within the GaP nanowires. To characterize the optical properties of the embedded quantum dots, they used 3-ps pulses of 430-nm light from a mode-locked Ti:sapphire laser to excite the dots and collected photoluminescence and photon correlation data on the response using a spectrometer, a streak camera and a pair of single-photon-counting avalanche photodiodes. The scientists attributed the high apparent brightness of the dots to the fact that they are not embedded in a high-refractive-index host material.

The ability to define the position of the quantum dots in the nanowire, they suggest, will be useful in the design of chainlike structures in which charges or photons are passed from one quantum dot to another.

Nano Letters, June 16, 2005, online article, doi:10.1021/nl050802y.