LEDs Emit Orange for White Light

Researchers at National Cheng Kung University, Chung Shan Institute of Science and Technology, Nan-Jeon Institute of Technology and Chin-Min College, all in Taiwan, have developed ZnCdSeTe-ZnSSe multiple-quantum-well LEDs that promise to enable phosphorless solid-state white-light illumination. They propose integrating the 578-nm emitter with a blue-green ZnSe-based LED on a substrate of GaAs to yield a single-chip source that does not rely on wavelength conversion.

They fabricated the LEDs in a P-down geometry on GaAs by molecular beam epitaxy. The final devices displayed an external quantum efficiency of only 0.08 percent, which they hope to improve by adopting an N-down scheme. The work appeared in the August IEEE Photonics Technology Letters.