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Terahertz pulse ups electron density by 1,000

Posted: 27 Dec 2011 ?? ?Print Version ?Bookmark and Share

Keywords:terahertz wave? photovoltaic cell? high-speed transistor?

A team of researchers from Kyoto University has announced a discovery that could clear the path for the development of ultra-high-speed transistors and high-efficiency photovoltaic cells. According to them, the terahertz pulse has dramatically boosted electron density.

Working with standard semiconductor material gallium arsenide (GaAs), the team observed that exposing the sample to a terahertz (1,000GHz) range electric field pulse caused an avalanche of electron-hole pairs (excitons) to burst. The single-cycle pulse, lasting merely a picosecond (10-12s), resulted in a 1,000-fold increase in exciton density compared with the initial state of the sample, they noted.

terahertz pulse

A picosecond terahertz pulse causes an avalanche of excitons to burst forth from GaAs. (Image from Tanaka Lab, Kyoto University).

"The terahertz pulse exposes the sample to an intense 1 MV/cm2 electric field," stated Hideki Hirori, team leader and assistant professor at Kyoto University's Institute for Integrated Cell-Material Sciences (iCeMS). "The resulting exciton avalanche can be confirmed by a bright, near-infrared luminescence, demonstrating a three-order of magnitude increase in the number of carriers."

Research in Kyoto using terahertz waves was led by Professor Koichiro Tanaka. "Since terahertz waves are sensitive to water, our goal is to create a microscope that will allow us to look inside living cells in real time," he reckoned.

"These just-released results using semiconductors are an entirely different field of science, but they demonstrate the rich potential that lies in the study of terahertz waves," stated Tanaka.

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