Researchers from Yale University have made
a light-emitting-diode that promises to lower the cost of integrating optical
communications and computer chips.
The device, made from the common semiconductor gallium arsenide,
emits 1.5-micron lightwaves, an important wavelength for transmitting signals
over the optical fibers of today's high-speed long distance communications
lines. The LED can emit one trillion light pulses per second.
The researchers' adapted gallium arsenide, which allows for fast
switching but usually emits shorter wavelengths, by engineering into the
material an energy band that allows it to emit the longer lightwaves. When
electrons drop from a high-energy band to a low one they give off light.
The researchers coaxed the material to form in a low-temperature
environment that caused an excess of arsenic atoms to grow on the gallium
lattice structure. This made for a material that contained an energy band
that allowed the material to emit light at room temperature at the 1.55-micron
wavelength required for long distance communications.
Practical applications for the light-emitting-diodes are possible
within three to five years, according to the researchers. The work appeared
in the May 4, 2003 issue of Nature Materials.
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