Incandescent bulbs are about 10 percent efficient, meaning they convert 10 percent of electricity into light and 90 percent into heat.
"Its actually a better heater than a light emitter," Sands said.
By comparison, efficiencies ranging from 47 percent to 64 percent have been seen in some white LEDs, but the LED lights now on the market cost about $100.
"When the cost of a white LED lamp comes down to about $5, LEDs will be in widespread use for general illumination," Sands said. "LEDs are still improving in efficiency, so they will surpass fluorescents. Everything looks favorable for LEDs, except for that initial cost, a problem that is likely to be solved soon."
He expects affordable LED lights to be on the market within two years.
Two remaining hurdles are to learn how to reduce defects in the devices and prevent the gallium nitride layer from cracking as the silicon wafer cools down after manufacturing.
"The silicon wafer expands and contracts less than the gallium nitride," Sands said. "When you cool it down, the silicon does not contract as fast as the gallium nitride, and the gallium nitride tends to crack."
Sands said he expects both challenges to be met by industry.
"These are engineering issues, not major show stoppers," he said. "The major obstacle was coming up with a substrate based on silicon that also has a reflective surface underneath the epitaxial gallium nitride layer, and we have now solved this problem."
|Contact: Emil Venere|