Reducing substitutional carbon in AlN LED substrates boosts deep-UV LED efficiency

May 15, 2012
Raleigh, NC--Researchers from North Carolina and Japan have developed a more-efficient UV LED potentially useful in sterilization of bacteria and viruses.

Raleigh, NC--Researchers from North Carolina and Japan have developed a more-efficient UV LED potentially useful in sterilization of bacteria and viruses.1 Using computer simulation, they determined that trace carbon atoms in the crystalline structure of the aluminum nitride (AlN) substrates used in UV LEDs were responsible for absorbing most of the relevant UV light. By eliminating the carbon in the substrate, the team was able to significantly improve the amount of UV light that can pass through the substrate at the desired wavelengths.

The 4.7 eV (265 nm) absorption band conventionally has an absorption coefficient of greater than 1000 cm-1; the researchers found that the absorption scaled linearly with the amount of substitutional carbon on the nitrogen site.

The technology has a wide array of applications ranging from drinking-water treatment to sterilizing surgical tools. “UV treatment utilizing LEDs would be more cost-effective, energy efficient and longer lasting,” says Ramón Collazo, an assistant professor of materials science and engineering at North Carolina State University. “Our work would also allow for the development of robust and portable water-treatment technologies for use in developing countries.”

The team also includes researchers from HexaTech (Morrisville, NC), Tokyo University of Agriculture and Technology, and the Tokuyama Corporation (also in Tokyo). Commercial technologies incorporating this research are currently being developed by HexaTech, a spin-off company from North Carolina State.

“This is a problem that’s been around for more than 30 years, and we were able to solve it by integrating advanced computation, materials synthesis and characterization,” says Doug Irving, assistant professor of materials science and engineering at North Carolina State. “I think we’ll see more work in this vein as the Materials Genome Initiative moves forward, and that this approach will accelerate the development of new materials and related technologies.”

REFERENCE:

1. Ramón Collazo et al., Applied Physics Letters 100, p. 191914 (2012); http://dx.doi.org/10.1063/1.4717623.

About the Author

John Wallace | Senior Technical Editor (1998-2022)

John Wallace was with Laser Focus World for nearly 25 years, retiring in late June 2022. He obtained a bachelor's degree in mechanical engineering and physics at Rutgers University and a master's in optical engineering at the University of Rochester. Before becoming an editor, John worked as an engineer at RCA, Exxon, Eastman Kodak, and GCA Corporation.

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