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Optoelectronics/Displays??

Researchers enhance green LED light output

Posted: 28 Apr 2011 ?? ?Print Version ?Bookmark and Share

Keywords:LED? green-colored LED? light extraction?

Researchers from Rensselaer Polytechnic Institute have found new method to manufacture green-colored LEDs with greatly enhanced light output. This new technique results in green LEDs with significant enhancements in light extraction, internal efficiency, and light output. This advancement is a critical step toward the development of LED televisions and displays.

The research team, led by Christian Wetzel, etched a nanoscale pattern at the interface between the LED's sapphire base and the layer of gallium nitride (GaN) that gives the LED its green color. The discovery brings Wetzel one step closer to his goal of developing a high-performance, low-cost green LED.

"Green LEDs are proving much more challenging to create than academia and industry ever imagined," Wetzel said. "Every computer monitor and television produces its picture by using red, blue, and green. We already have powerful, inexpensive red and blue LEDs. Once we develop a similar green LED, it should lead to a new generation of high-performance, energy-efficient display and illumination devices. This new research finding is an important step in the right direction."

Green LED

Etching a nanoscale pattern at the interface between the LED's sapphire base and GaN layer gives it its green color.

Wetzel is a professor of physics and Wellfleet Constellation professor of Future Chips at Rensselaer.

Sapphire is among the least expensive and widely used substrate materials for manufacturing LEDs, so Wetzel's discovery could hold important implications for the rapidly growing, fast-changing LED industry. He said this new method should also be able to increase the light output of red and blue LEDs.

LED lighting only requires a fraction of the energy required by conventional light bulbs, and LEDs contain none of the toxic heavy metals used in the newer compact fluorescent light bulbs. In general, LEDs are very durable and long-lived.

First discovered in the 1920s, LEDs are semiconductors that convert electricity into light. When switched on, swarms of electrons pass through the semiconductor material and fall from an area with surplus electrons into an area with a shortage of electrons. As they fall, the electrons jump to a lower orbital and release small amounts of energy. This energy is realized as photonsthe most basic unit of light. Unlike conventional light bulbs, LEDs produce almost no heat.


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