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Low-Cost LED Lighting Advances

Low-Cost LED Lighting Advances

Breakthrough by Purdue University could help reduce energy consumption.

Researchers at Purdue University say they have overcome an obstacle to producing low-cost LED lighting. LED, or light-emitting diode, lighting is touted as more energy efficient than incandescent lighting and contains no mercury like that found in compact fluorescent lights.

The expense of LED lights, the researchers say, is due in part to their creation on a substrate of sapphire. The Purdue researchers have developed an alternate method to create this solid-state lighting, one that instead relies on metal-coated silicon wafers.

The use of silicon will allow industry to manufacture many devices on large wafers of silicon, thus reducing costs, says Purdue's Timothy D. Sands, professor of materials engineering and electrical and computer engineering. The silicon also dissipates heat better than sapphire, he reports.

Timothy D. Sands, left, director of Purdue's Birck Nanotechnology Center, and graduate student Mark Oliver, operate a "reactor" in work aimed at perfecting solid-state lighting.
In addition, "If you replaced existing lighting with solid-state lighting, following some reasonable estimates for the penetration of that technology based on economics and other factors, it could reduce the amount of energy we consume for lighting by about one-third," Sands says.

Hurdles remain in bringing this new technology to market, including determining how to reduce defects in the devices and preventing the gallium nitride layer from cracking as the silicon wafer cools after manufacturing. Gallium nitride, a compound used in LEDs, contracts at a faster rate than silicon, leading to a tendency to crack.

"These are engineering issues, not major show stoppers," Sands says. "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."

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