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Follow the light

Field-effect transistors incorporating a single germanium nanowire can detect visible light with a high level of sensitivity

Credit: © 2007 AIP

High-aspect-ratio nanoscale semiconducting structures with diameters of less than 100 nm and lengths in the micrometre range are being investigated for use as emitters and detectors of polarized light. In particular, nanowires made from wide-bandgap semiconductors, such as zinc oxide, have been demonstrated to be highly efficient photodetectors of ultraviolet light.

Although studies focusing on visible light detection have shown that large arrays of germanium nanowires exhibit photoconductivity, there have been no reports to-date on this phenomenon in the context of individual Ge nanowires. Now, Jiwoong Park from the Rowland Institute at Harvard in the US and Y. H. Ahn from Ajou University, Suwon in Korea, report that single Ge nanowires are highly efficient polarization-sensitive photodetectors when illuminated — even at relatively low intensities — with 532-nm visible laser light1 .

The p-type Ge nanowires were made from GeH4 diluted in H2 by a multistep chemical vapour deposition process using 30-nm-diameter gold clusters as catalysts. A single Ge nanowire, 50 nm in diameter, was then deposited on an oxide layer, and source/drain contacts were defined — in a field-effect transistor configuration — with titanium metal. The photoconductivity of a single Ge nanowire was shown to be more than two orders of magnitude greater than a similar nanowire made from silicon.


  1. Ahn, Y. H. & Park, J. Efficient visible light detection using individual germanium nanowire field effect transistors. Appl. Phys. Lett. 91, 10.1063/1.2799253 162102 (2007).

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Sandhu, A. Follow the light. Nature Nanotech (2007).

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