High-efficiency UV LEDs using quaternary InAlGaN.

High-efficiency ultraviolet (UV) light sources are very attractive for application to the medical field, white lighting, high-density memories, and so on. We have demonstrated that 300- to 370-nm UV emission is considerably enhanced by the introduction of several percent of In into AlGaN due to an In-segregation effect. We fabricated 310-nm-band UV LEDs with quaternary InAlGaN emitting layers on a sapphire substrate and obtained submilliwatt output power. We also fabricated 350-nm-band InAlGaN-based quantum-well LEDs on GaN substrates in order to eliminate the effects of threading dislocations. The maximum UV output power obtained was as high as 7.4 mW under room-temperature CW operation. The maximum external quantum efficiency (EQE) was 1.1% with an injection current of 50 mA, which is the highest EQE ever obtained for 350-nm-band UV LEDs with top-emission geometry. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 157(3): 43–51, 2006; Published online in Wiley InterScience (<URL>www.interscience.wiley.com</URL>). DOI 10.1002/eej.20287 Copyright © 2006 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]