Purdue brings us one big step closer to cheap LEDs

July 17, 2008   by Jozef Winter

LEDs, light-emitting diodes, are the future of household and commercial lighting, there is no doubt about that; they are way more efficient than even compact fluorescent bulbs (they also contain no mercury), use very little electricity, and last about 50,000 hours, meaning they’ll probably outlive us all. The question though, is when we’ll actually see them on the shelves next to the old news CFLs. The problem has been their cost. While you can get them, you’re probably looking to shell out around $30-50 for a single “bulb” that will put out the same light as a 60-watt incandescent, and well, that’s a tough sell for consumers. Researchers at Purdue university, however, have come up with a solution.

LEDs use a material called gallium nitride to create light, but unfortunately the current processes cost at least 20 times more than incandescents and CFLs to produce the same light output. The problem is that when LEDs shine, some of their light is lost, as the light will travel upwards into the bulb. A reflective surface would solve that problem but their reflecting surface, made of zirconium nitride, becomes unstable when in contact with silicon, causing a chemical reaction. By placing a layer of aluminum nitride between the two metals, they were able to solve that problem and redirect the light emitted to where it is needed.

The technique to accomplish this is quite complex, but common in the electronics industry. With this “reactive sputter deposition”,

“the researchers bombarded the metals zirconium and aluminum with positively charged ions of argon gas in a vacuum chamber. The argon ions caused metal atoms to be ejected, and a reaction with nitrogen in the chamber resulted in the deposition of aluminum nitride and zirconium nitride onto the silicon surface. The gallium nitride was then deposited by another common technique known as organometallic vapor phase epitaxy, performed in a chamber, called a reactor, at temperatures of about 1,000 degrees Celsius, or 1,800 degrees Fahrenheit.”

As complicated as that sounds, the good news is that with improvements such as this, LEDs will no doubt become cheaper in the years to come and reduce some of the 101 billion kWh used to light the United States every year.

via physorg