Ultraviolet light emitting diodes

Abstract

The paper presents a review of the recent development of III-nitride based deep UV light emitting diodes (LEDs). Main applications of the deep UV LEDs are introduced. Review of material issues is focused on the lattice mismatch between the substrate and the active layer and at heterojunctions in multiple quantum well structures forming the active layer, the localization of nonequilibrium carriers, the material properties limiting the internal quantum efficiency, and the effect of efficiency droop at high density of nonequilibrium carriers. AlGaN is currently the semiconductor of choice for development of deep UV LEDs, so this material is the most discussed one in this review, though some information on AlInGaN is also provided.

Uridine as Photochemical Actinometer: Application to Led-Uv Flow Reactors

“…These devices are essentially solid-state semiconductor-based systems which, when appropriately designed and electrically powered, are able to transform electric current in photons. 7 Commercially-diffused LEDs are able to emit light in the visible and are characterized by a very long life of the order of 25000-100000 h, against only 1500-8000 h of mercury vapor lamps. 2,7,[8][9][10] In addition, LEDs are very low energyconsuming systems.…”

“…7 Commercially-diffused LEDs are able to emit light in the visible and are characterized by a very long life of the order of 25000-100000 h, against only 1500-8000 h of mercury vapor lamps. 2,7,[8][9][10] In addition, LEDs are very low energyconsuming systems. For example, a common 4000 Lumen visible light source requires 300 W from a classic incandescent bulb with tungsten filament, about 100-200 W with modern compact fluorescence lamps and only 40 W from a LED source.…”

“…These LED-UV sources are based on semiconductor materials made of galliumaluminum nitrides or gallium-indium-aluminum nitrides, through which it is possible to approach or reach the wavelengths normally emitted by low-pressure mercury vapor sources, the UV-C, which is the wavelength range commonly used for photochemical reactions and water disinfection. [7][8][9][10] More in detail, low-pressure mercury vapor lamps emit almost exclusively about 254 nm and it is not practically possible to change the position of the emission line due to an electronic mercury transition. Instead, LED-UV sources can be suitably configured to operate in the desired wavelength in the UV.…”

The effect of free-standing GaN substrate on carrier localization in ultraviolet InGaN light-emitting diodes

“…The InGaN-based ultraviolet light-emitting diodes (UV-LEDs) with wavelength ranging from 350 to 400 nm have received enormous attention for practical application, such as bio-sensor, high density storage, and short-haul optical communication [1, 2]. Besides, the white-light LEDs (WLEDs) can be realized by using InGaN-based UV-LED chip which excited the phosphor of red, green, and blue (RGB) [3].…”

UV-LEDs Efficiently Inactivate DNA and RNA Coliphages

“…The emitting wavelengths can be tailored with the choice of materials. Aluminum gallium nitride and aluminum nitride are the most used materials [7,8].…”