HOUSTON -- (Dec. 8, 2010) -- Physicists from Rice University and Princeton University have discovered how to use one of the information technology industry's mainstay materials -- gallium arsenide semiconductors -- as an ultrasensitive microwave detector that could be suitable for next-generation computers. The discovery comes at a time when computer chip engineers are racing both to add nanophotonic devices directly to microchips and to boost processor speeds beyond 10 gigahertz (GHz).
"Tunable photon-detection technology in the microwave range is not well-developed," said Rice physicist Rui-Rui Du, the study's lead author. "Single-photon detectors based on superconductors in the 10-GHz to 100-GHz range are available, but their resonance frequency has been difficult to tune. Our findings suggest that tunable single-photon detection may be within reach with ultrapure gallium arsenide."
The study, which is available online and due to appear in print this week in Physical Review Letters, is the latest result from a long-term collaboration between Du and Princeton University physicist Loren Pfeiffer, whose group produces the world's purest samples of gallium arsenide. For the new study, Rice graduate student Yanhua Dai cooled one of Pfeiffer's ultrapure samples to below 4 degrees Kelvin -- the temperature of liquid helium. She then bombarded the sample with microwaves while applying a weak magnetic field -- approximately the same strength as that of a refrigerator magnet. Du and Dai were surprised to find that microwaves of a specific wavelength resonated strongly with the cooled sample. They also found they could use the magnet to tune this resonance to specific microwave frequencies.
Du said previous experiments have typically measured weak resonance effects from microwaves. "A signal level of 1 percent is a common measurement. In our case, the change was a thousand times that much."
While the team does not yet understa
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