The band gap and wavelength of AlGaN materials are related to the Al composition.
The ultraviolet spectrum ranges from 100 to 400 nm and is generally subdivided into three segments: UV-A long-wave ultraviolet (315 to 400 nm), UV-B medium-wave ultraviolet (280 to 315 nm), and UV-C short-wave ultraviolet (200 to 280 nm). ) and ultra-deep ultraviolet (100 to 200 nm). Since ultraviolet light has a shorter wavelength than visible light, when the wavelength is reduced to 365 nm, a direct bandgap semiconductor material having a forbidden band width greater than 3.4 eV has been required as a base material for the device. Among the current wide-bandgap semiconductor materials, AlGaN is an ideal material for realizing this wavelength source, and its emission wavelength can cover 210-365 nm ultraviolet light (as shown). Therefore, AlGaN-based UV LEDs are the most ideal alternative source for UV light.
Some foreign research teams have started research on near-ultraviolet LEDs very early. In 1997, Philips' PMMensz produced near-ultraviolet LEDs with luminescence wavelengths of 385 nm and 412 nm with an optical output power of 1.5 mW. The following year, MukaiT et al. of Nichia Corporation adopted the InGaN/AlGaN structure in the quantum well region of the LED, and successfully developed an ultraviolet LED with an output power of 5 mW, which has an emission wavelength of 371 nm and an external quantum efficiency (EQE) of 7.5%. In 2001, the Japanese Photonics Laboratory used MOPVE lateral epitaxial growth technology (LEO) to develop a near-ultraviolet LED with an emission wavelength of 382 nm and an optical output power of 15.6 mW at a 20 mA injection current, with an external quantum efficiency of 24%. In 2002, the 400nm near-ultraviolet LED developed by Japan's Motokazu Yamada et al., the optical output power was 22mW at 20mA injection current, and the external quantum efficiency was 35.5%. In 2005, DSWuu et al. grew on a graphic sapphire substrate. The 410nm near-ultraviolet LED has an optical power and external quantum efficiency of 10.4mW and 14.1% at 20mA injection current respectively. In 2008, H Sakuta et al. reported 405nm near-ultraviolet LED from Japan's Changzhou Company, and the external quantum at 20mA. The efficiency reached 46.7%.
The application of current UV LEDs has been involved in various fields. In addition to the common use of ultraviolet LEDs to stimulate RGB phosphors in the field of illumination, the deep ultraviolet illumination band below 300 nm can also be applied to UV identification, sterilization, liquid detection and analysis. In other fields, 300-400nm ultraviolet light can be applied in the fields of medical light therapy, polymer and ink printing technology, and identification.
Ultraviolet LEDs have obvious advantages in terms of performance. Ordinary ultraviolet light sources require an external lens to achieve sufficient brightness and uniformity of the emitted light. The light emitted by the ultraviolet LED has the characteristics of high brightness, high concentration, low energy consumption and long service life.
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