A team led by Professor Cho Yong-Hoon of the Department of Physics developed a phosphor-free white LED manufacturing technology. White LEDs can be obtained using a single semiconductor chip without any phosphors. Existing white LEDs combine various LED chips, or combine blue LED with yellow phosphor coating. Phosphors are often rare earth compounds that have to be imported, and the combination of various LED chips is expensive. The team designed three-dimensional gallium nitride structures with truncated hexagonal pyramids. The three-dimensional structures offer multi-quantum wells, and different colored light can be produced on each side. Instead of combining various LED colors, this method allows different colors to be mixed within a single structure. The team explained that white LEDs can be produced by varying the time and conditions used to fabricate the three-dimensional structures to achieve different facet areas. Professor Cho said, «We developed phosphor-free white LEDs using a single LED chip by adjusting the area of each facet. The color remains the same even when the LED is subject to different current levels. This study is significant in that it has demonstrated the potential of phosphor-free white LEDs.» He added, «By improving the efficiency through the three-dimensional semiconductor process, single-chip phosphor-free white LEDs with good color representation can be utilized as a light source.» The results were published online in Light: Science & Applications, a journal of the Nature Publishing Group, on February 12.
