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5 December 2013 11:26 am ,
Vol. 342 ,
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
Since arriving on the island of Guam in the 1940s, the brown tree snake ( Boiga irregularis ) has extirpated native...
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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Blue-Blood Semiconductors on Low-Rent Silicon
24 January 2000 7:00 pm
Researchers trying to coax light from semiconductors have a case of the blues, but they couldn't be happier. A team has found a better way to build blue light-emitting diodes (LEDs) on a base of silicon, the cheap and ubiquitous substrate for microelectronics. The success, described in the 17 January issue of Applied Physics Letters, brings the technology closer to a world of possible applications, including a chip-sized replacement for the light bulb.
The garden-variety light bulb, little changed over the last century, costs just pennies to produce but is expensive to run. It pushes electricity through a tungsten filament, turning it white hot and producing soft white light--and a lot of wasted heat. Newer compact fluorescent lights do better, but LEDs have the potential to put them all in the shade. Because semiconducter chips made of gallium nitride generate far less heat, they could be almost 17 times as efficient as light bulbs. For the past several years researchers have managed to cajole semiconductor devices into emitting blue light when pumped with electricity. But blue semiconductor lights are still too expensive for general lighting, in part because they're grown on expensive substrates such as sapphire. So teams have searched for a way to make blue LEDs work on cheap silicon.
Early success came in the last couple of years from researchers at IBM and Emcore Corp., who used different methods to deposit their light emitters. But these devices still suffered flaws that limited their efficiency. Now, Asif Khan of the University of South Carolina, Columbia, and his colleagues report better results by combining the earlier techniques. They first laid down a buffer of aluminum nitride and then grew the gallium nitride on top. They also were able to place the gallium nitride only where they wanted it--a patterning technique that opens up the possibility of making full-color gallium nitride LED displays.
The new LEDs atop silicon aren't yet as bright as those grown on sapphire. Still, "it's a good development," says Fred Schubert, an electrical engineer at Boston University in Massachusetts. "Silicon substrates are cheap and big. So if a silicon LED technology succeeds, it would mean the technology could be very cheap."