PORTLAND, Ore. Excitonic transistors could solve the persistent problem of electronically switching optical communications signals, but until now have required very expensive supercooling. Now, researchers have refined the materials mix and architecture of excitonic transistors to permit economical operation at 125 degrees Kelvin, which they say is attainable with inexpensive liquid nitrogen.
"We have shown that by refining the architecture and going to other materials we can raise the temperature at which excitonic circuits will work," said professor Leonid Butov of the University of California at San Diego. "Our next milestone will not be room- temperature operation yet, but we do have plans for operation at even higher temperatures...in the near future."
Unlike conventional electronic circuits, exitonic transitors automatically convert optical signals into excitons--bound electron-hole pairs. After processing the excitons with conventional signal processing techniques, the electron-hole pairs are recombined, thereby emitting an photon at the output of the circuit.
In this way, excitronic circuitry eliminates the conventional optical-to-electronic and electron-to-optical converters required for conventional opto-electronic switching devices.
The architecture used by the researchers combined many thin layers of gallium arsenide and aluminum arsenide in a coupled quantum well structure in which bound electron-hole pairs were held in adjacent quantum wells 4 nanometers apart. Using this configuration, the researcher demonstrated an exciton-based optoelectronic transistor, an excitonic bridge modulator and an excitonic pinch-off modulator.
Next, the researchers said they will seek to develop room-temperature exitonic transistors by again refining materials and architecture.
Research funding was provided by the U.S. Army Research Office, the U.S. Energy Department and the National Science Foundation.