Recently, the researchers at Purdue University say they have overcome an obstacle to producing low-cost LED lighting. LED 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 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, the silicon also dissipates heat better than sapphire, says Purdue's Timothy D. Sands, professor of materials engineering and electrical and computer engineering. He and his team operate a "reactor" in work aimed at perfecting solid-state lighting.
In addition, based on economics and other factors, if existing lighting replaced by solid-state lighting, following some reasonable estimates for the penetration of that technology it could reduce the amount of energy consume for lighting by about one-third. 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.
Based on silicon, the major obstacle was coming up with a substrate that also has a reflective surface underneath the epitaxial gallium nitride layer, and the Purdue researchers have now solved this problem.
