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Research: Novel coating boosts LED brightness, resilience

Posted: 24 Mar 2014 ?? ?Print Version ?Bookmark and Share

Keywords:North Carolina State University? LED? GaN? phosphonic?

Researchers from North Carolina State University have developed a processing technique that makes light emitting diodes (LEDs) brighter and more resilient. They were able to do this by coating the semiconductor material gallium nitride (GaN) with a layer of phosphorus-derived acid.

"By coating polar GaN with a self-assembling layer of phosphonic groups, we were able to increase luminescence without increasing energy input," explained Stewart Wilkins, a Ph.D. student at North Carolina State University. "The phosphonic groups also improve stability, making the GaN less likely to degrade in solution. Making the GaN more stable is important because that makes it more viable for use in biomedical applications, such as implantable sensors."

The researchers started with polar GaN, composed of alternating layers of gallium and nitrogen. To increase luminescence, they etched the surface of the material with phosphoric acid. At the same time, they added phosphonic groups, organic molecules containing phosphorus that self-assembled into a monolayer on the surface of the material. The layer further increased luminescence and improved the stability of the GaN by making it less likely to react chemically with its environment.

Increasing LED brightness

By coating polar gallium nitride with phosphonic groups, the North Carolina State University researchers increased luminescence without increasing energy input. (Image: Stewart Wilkins)

Senior author of the paper is Albena Ivanisevic, an associate professor of materials science and engineering at NC State and associate professor of the joint biomedical engineering program at NC State and the University of North Carolina at Chapel Hill. The paper was co-authored by Consuelo Arellano, a research associate professor of statistics at NC State; Tania Paskova, a research professor of electrical and computer engineering at NC State; and Michelle Greenough, an undergraduate at Wagner College.

- Paul Buckley
??EE Times Europe

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