Credit: © 2008 AAAS

Integrated circuits might one day be based on the exciton — a bound state of an electron and a positive ‘hole’ — rather than the electron. An exciton can be created when an electron is excited, usually by a photon, from the valence band of a semiconductor to the conduction band, leaving a hole behind. Leonid Butov and co-workers1 at UC San Diego and UC Santa Barabara have now performed simple circuit operations on excitons for the first time.

Excitons have no net charge, so they are not very sensitive to electron fields, and they usually have lifetimes shorter than one nanosecond. Butov and co-workers overcame these obstacles in a new excitonic integrated circuit comprising three exciton transistors. The circuit operates with ‘indirect’ excitons in which the electron and the hole are separated by a short distance, resulting in an electric dipole moment and a longer lifetime.

The circuits can be regarded as performing electronic operations on photons, using excitons as an intermediate media. This new branch of optoelectronics could improve the interactions between photon signals and integrated circuits, and allow the further miniaturization of devices.