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Deep Ultraviolet LED Technology for Public Health and Purification

Nov. 17, 2020

The new coronavirus SARS-CoV-2 (previously known as 2019-nCoV) causes the 2019 coronavirus disease (COVID-19) and is now raging around the world. The world is paying special attention to finding ways to fight this new type of coronavirus. This includes the Solid State Lighting and Energy Electronics Center (SSLEEC) and member companies of the University of California, Santa Barbara. Researchers, there are developing ultraviolet light-emitting diodes (LEDs) in order to be able to remove the surface of the object ---potentially air and water ---contaminated by exposure to SARS-CoV-2.

Christian Zollner, a Ph.D. researcher in materials at the University of California, Santa Barbara, said, “One of the main applications is in the medical field---disinfecting personal protective equipment, surfaces, and floors in HVAC systems.” His work focuses on promoting the use of Deep ultraviolet LED technology for public health and purification. He added that in the medical field, the market for UV-C disinfection products is already small.

Indeed, people are beginning to pay attention to the inactivation effect of ultraviolet rays on this new type of coronavirus. As a technology, UV disinfection has been around for some time. Although practical, it has not yet shown the effect of preventing the spread of SARS-CoV-2 on a large scale. Ultraviolet light has many prospects: SSLEEC member company Seoul Semiconductor reported in early April that their ultraviolet LED products "disinfect SARS-CoV-2 by 99.9% within 30 seconds." Their technology is currently being used in automobiles to disinfect the interior of unused vehicles in UV LED lights.

It is worth noting that not all UV wavelengths are the same. Ultraviolet A (UV-A) and Ultraviolet B (UV-B) have important uses. On the earth, they are mostly obtained from the sun’s rays, but ultraviolet C (UV-C) is relatively rare and is used to purify the air and UV is the first choice for water and to inactivate microorganisms. UV-C can only be produced through manual processes.

Zollner said, "UV-C in the range of 260 to 285nm, which is most relevant to current disinfection technology, is also harmful to human skin. Therefore, it is currently mainly used for disinfection in an environment where no one is." In fact, the World Health Organization ( WHO) warns against using ultraviolet disinfection lamps to disinfect hands or other areas of the skin. Even brief exposure to UV-C light may cause burns and eye damage.

Before the COVID-19 epidemic broke out globally, materials scientists from SSLEEC were already studying UV-C LED technology. This area of the electromagnetic spectrum is a relatively new frontier in solid-state lighting. Zollner believes that UV-C is usually produced by mercury vapor lamps, "it requires many technological advances to make UV LEDs to realize their potential in terms of efficiency, cost, reliability, and service life."

UVA Led Series

In a new study, researchers from SSLEEC report a more elegant method of manufacturing high-quality deep ultraviolet (UV-C) LEDs, which involves the deposition of semiconductor alloy nitride on silicon carbide (SiC) substrate Aluminum gallium (AlGaN) film, which is different from the more widely used sapphire substrate. The related research structure was recently published in the journal ACS Photonics with the title of the paper "AlGaN deep-ultraviolet Light-Emitting Diodes Grown on SiC Substrates".

Zollner believes that compared to using sapphire, using silicon carbide as a substrate can grow high-quality UV-C semiconductor materials more efficiently and economically. He explained that this is because the atomic structures of these materials match very closely.

He said, "According to general experience, the more similar the substrate and the semiconductor film in structure (in terms of atomic crystal structure) to each other, the easier it is to obtain high-quality materials." The better the quality, the better the efficiency and performance of the LED. Sapphire is structurally different, and the production of flawless and misaligned materials usually requires complicated additional steps. Zollner said that silicon carbide is not a perfect match, but high quality can be achieved without expensive additional steps.

In addition, according to Zollner, silicon carbide is much cheaper than the "ideal" aluminum nitride substrate, making it easier to mass-produce.

When these researchers developed their UV-C LED technology, portable, fast-acting water disinfection was one of the main applications they considered; the durability, reliability, and compact form factor of this diode would be less clean than those in the world. Underdeveloped areas of water trigger changes.

The emergence of the COVID-19 epidemic has added another level of application. With the search for vaccines, drugs, and cures for this disease worldwide, disinfection, decontamination, and isolation are the few weapons we can protect ourselves, and these solutions will need to be promoted globally. Zollner said that in addition to UV-C for water sanitation purposes, UV-C can also be integrated into systems that are turned on when no one is present.

He said: "This will provide a low-cost and convenient method without the use of chemicals for the disinfection of public, retail, personal and medical places."

But for now, we need to wait patiently, because Zollner and his colleagues are waiting for the end of the epidemic. At the University of California, Santa Barbara, in order to minimize contact between people, research progress in this area has been slowed down.

He said, "Once the research activities carried out at the University of California, Santa Barbara resume, our next step is to continue to improve our AlGaN/SiC platform to hopefully produce the world's most efficient UV-C emitter."