New technique to transform low-energy light detection

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A way to use standard semiconductors to detect light over a much broader range of wavelengths has been discovered. The technology, developed by a team of scientists at Georgia State University in the United States and the University of Leeds in the UK, opens up new possibilities in solar power generation and low-energy light detection.

Until now, one of the solutions to the challenge of detecting low-energy light has been to find special semiconductor materials that respond to it. The new approach, published in the April issue of Nature Photonics, extends the range of existing semiconductors rather than relying on novel materials. Because no novel materials are required, this technique offers the potential for wafer-scale integration with electronic devices.

To do this, the researchers added a second light source, which primes the semiconductor with energy so that when the low-energy wavelengths arrive they can generate a current.

The device can detect wavelengths up to at least the 55µm range. Previously, the same detector could only see wavelengths of approximately 4µm. The team has also run simulations showing that a refined version of the device could detect wavelengths up to 100µm long.

Edmund Linfield, professor of Terahertz Electronics in the University of Leeds' School of Electronic and Electrical Engineering, whose team built the patterned semiconductors used in the new technique, commented: ‘Generating electric current from the lower energy ranges of the electromagnetic spectrum, such as infrared, is very challenging using semiconductor materials because the wavelengths involved provide little energy. We are extremely excited about finding a way to address this problem.

‘The pay-offs are potentially very significant, from more efficient use of solar energy by utilising a larger portion of the spectrum to developing new types of detector for use at long wavelengths.’

Professor Unil Perera, head of Georgia State University’s Optoelectronics Research Laboratory, which led the study, added: ‘This technology will also allow dual or multiband detectors to be developed, which could be used to reduce false positives in identifying – for example – toxic gases.’