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SUMMARY Deep-ultraviolet (DUV) light-emitting diodes (LEDs) are in demand for a wide variety of potential applications, such as sterilization, water and air purification, medical uses, and so on. We have demonstrated 222-351 nm AlGaN and quaternary InAlGaN-based DUV-LEDs by developing a low threading dislocation density (TDD) AlN crystal. We achieved an external quantum efficiency (EQE) of about 4% and an output power greater than 30 mW in DUV-LEDs for use in sterilization applications by developing new crystal growth techniques. [ABSTRACT FROM AUTHOR]

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 (www.interscience.wiley.com). DOI 10.1002/eej.20287 Copyright © 2006 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Aluminium gallium nitride (AlGaN)‐based ultraviolet‐B light‐emitting diodes (UVB LEDs) are expected to offer smart size, wider choice of UVB light emission in the wavelengths range of 280 nm > λ > 320 nm, and low cost as well as low power consumption compared with other UV light sources including toxic mercury UV‐lamps. The hole‐tunneling from p‐AlGaN side of UVB LED into the multi‐quantum‐wells (MQWs) is strongly dependent on the thickness (TFB) and Al‐contents of undoped (ud)‐AlGaN final barrier (FB). Herein, the photoluminescence (PL) efficiency from MQWs of the UVB LED devices is investigated and compared with the electroluminescence (EL) spectra as a function of TFB. Subsequently, the dependence of PL efficiency, external quantum efficiency (EQE), and light output power on the TFB of UVB LEDs is attempted, using the same growth condition for all samples except variation in TFB. When TFB is set to 6–7 nm, improvements in the EQE and light output power, respectively, from 4.3% and 7 mW to the high values of 5.6% and 17 mW in emission band of 295–300 nm under continuous‐wave (cw) at room temperature (RT) are achieved. [ABSTRACT FROM AUTHOR]