A relatively simple and inexpensive solution to the problem of ultraviolet light-absorption in LED substrates will enable the development of LED devices that use UV light to kill pathogens such as bacteria and viruses. Researchers at North Carolina State University, led by Ramón Collazo, an assistant professor of materials science and engineering, determined that trace carbon atoms in the structure of aluminum nitride (AlN) – the semiconductor material of which most LEDs are made because of its power and versatility - absorbed most of the UV light passing through the material. Improving the amount of UV light allowed through was as simple as removing the stray carbon atoms. UV light at wavelengths between 185 and 264 nm causes defects in the thymine molecules in pathogen DNA. Once enough of these defects accumulate, the pathogens can no longer replicate and become effectively harmless. “UV treatment utilizing LEDs would be more cost-effective, energy efficient and longer lasting,” Collazo said. “Our work would also allow for the development of robust and portable water-treatment technologies for use in developing countries.” An NC State spinoff, HexaTech Inc., has begun developing the research into commercial technology. “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,” said Doug Irving, Collazo's colleague at NC 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.” The research was published online in Applied Physics Letters. Co-authors are Benjamin Gaddy, Zachary Bryan, Ronny Kirste and Marc Hoffman, all from NC State, and researchers from HexaTech, Tokyo University of Agriculture and Technology, and Tokuyama Corp. The research was funded by the US Department of Defense. For more information, visit: www.ncsu.edu