The killer's UV-C UV light, with a wavelength of only 200 to 280 nm, is high in energy and can penetrate the membranes of viruses, bacteria, fungi and dust mites, attack DNA and destroy these harmful organisms.
Since Danish professor Niels Finsen discovered that ultraviolet radiation can treat tuberculosis, humans have been using UV sterilization for more than a hundred years. However, the deep ultraviolet lamps currently used are not only bulky and inefficient, but also contain mercury, which is harmful to the environment.
The research team of Cornell University has recently developed a small and more environmentally-friendly deep ultraviolet LED light source, and set a record for the lowest wavelength of the industry's deep-UV LED.
The researchers used a single-layer film of gallium nitride (GaN) and aluminum nitride (AlN) as the reaction area at the atomic-level control interface to successfully emit deep-UV LEDs with wavelengths ranging from 232 to 270 nm. This 232 nm deep ultraviolet light hits the record with the shortest wavelength of light emitted by using gallium nitride as the luminescent material. The previous record was 239 nm set by the Japanese team.
The picture shows the research team members, photo source: Cornell University
The research paper "MBE-grown 232-270nm deep-UV LED susing monolayer thin binary GaN/AlN quantum heteros tructures" was published on January 27th in the "Applied Physics Letters" website.
Improve UV LED efficiency
At present, the biggest bottleneck of UV LEDs is luminous efficiency, which can be measured in three aspects:
1. Injection efficiency: The ratio of electron passing devices injected into the reaction zone.
2. Internal quantum efficiency (IQE): The proportion of all electrons in the reaction zone that produce photons or ultraviolet light.
3. Light extraction efficiency: The proportion of photons produced in the reaction zone, which can be taken out of the device and made available.
One of the authors, Dr. (Moudud) Islam, said: "If the efficiency of the above three aspects is 50%, the multiplication is only one-eighth, which is equivalent to the luminous efficiency has dropped to 12%."
In the deep ultraviolet range, the efficiency of these three aspects is very low, but the research team found that the use of gallium nitride instead of the traditional aluminum gallium nitride can improve the internal quantum efficiency and light extraction efficiency.
In order to improve the injection efficiency, the research team used the previously developed technology to implement the polarization induction doping method in the positive (electron) and negative (hole) carrier regions.
research Development
After successfully improving the luminous efficiency of deep-UV LEDs, the next step for the research team is to integrate the light source into the device and move toward the goal of going public. The application fields of deep ultraviolet light include food preservation, counterfeit banknote discrimination, photocatalyst, water purification and sterilization.
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