Exciton-based circuits to enable faster computing

June 20th, 2008 - 3:36 pm ICT by IANS  

Washington, June 20 (IANS) Particles called excitons that emit a strong pulse of energy as they decay could soon enable a new and faster mode of computing, according to a study. Transistors - the building blocks for all electronic devices - use electrons to ferry signals needed for computation. But almost all computation devices use light, or photons, to send signals.

The need to convert the signalling language from electrons to photons limits the speed of electronic devices.

Now, University of California researchers have built transistors that process signals using excitons - which, like electrons, can be controlled with electrical voltages but, unlike electrons, transform into photons at the output of the circuit.

“This direct coupling of excitons to photons bridges a gap between computing and communications,” said Leonid Butov, who led the study.

Excitons are created by light in a semiconductor, which separates a negatively charged electron from a positively charged “hole”. When the electron recombines with the hole, the exciton decays and releases its energy as a flash of light.

Butov and his colleagues have used a special type of exciton where the electron and its hole are confined to different areas. This configuration creates an opportunity to control the flow of excitons using voltage supplied by electrodes.

These voltage gates create an energy bump that can halt the movement of excitons or allow them to flow. Once that energy barrier is removed, the exciton can travel to the transistor output and transform to light, which could be fed directly into a communication circuit, eliminating the need to convert the signal.

“Excitons are directly coupled to photons, which allows us to link computation and communication,” Butov said.

These findings have been reported in the online version of the journal Science.

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