Researchers at the University of California, Santa Barbara (UC Santa Barbara) are developing ultraviolet (UV) LEDs for decontaminating surfaces and potentially air and water that have come in contact with the SARS-CoV-2 virus.
UVC is the UV wavelength that is used for purifying air and water and for inactivating microbes. Unlike UVA and UVB wavelengths, UVC can be generated only through inorganic processes.
The materials scientists at UC Santa Barbara’s Solid State Lighting & Energy Electronics Center (SSLEEC) were already working on UVC LED technology when the COVID-19 pandemic gained momentum. The researchers fabricated high-quality deep-UVC LEDs by depositing a film of the semiconductor alloy aluminum gallium nitride (AlGaN) on a substrate of silicon carbide (SiC), in a departure from the more widely used sapphire substrate.
According to researcher Christian Zollner, using SiC as a substrate allows for more efficient growth of high-quality UVC semiconductor material than sapphire, because the atomic structure of SiC closely matches that of AlGaN. “As a general rule of thumb, the more structurally similar (in terms of atomic crystal structure) the substrate and the film are to each other, the easier it is to achieve high material quality,” he said. The higher the quality, the better the LED’s efficiency and performance. SiC is not a perfect match, Zollner said, but it enables the material to be high-quality without the need for costly, additional methods. Also, it is less expensive than the “ideal” aluminum nitride substrate, making it more mass-production-friendly.
The researchers initially envisioned their UVC LEDs being used as portable, fast-acting water disinfectants in areas in the world where clean water is scarce. The COVID-19 pandemic led them to consider the technology’s potential as a disinfectant and decontaminant for the virus. In addition to UVC LEDs for water sanitation purposes, UVC LEDs could be integrated into systems that turn on when no one is present, Zollner said. “This would provide a low-cost, chemical-free, and convenient way to sanitize public, retail, personal, and medical spaces,” he said.
While the large-scale efficacy of UVC against the spread of SARS-CoV-2 has yet to be shown, Seoul Semiconductor, an SSLEEC member company, in early April 2020 reported a “99.9% sterilization of coronavirus (COVID-19) in 30 seconds” with their UV LED products. The company’s technology is currently being adopted for UV LED lamps that sterilize the interior of unoccupied vehicles.
For the moment, Zollner and his team must wait out the pandemic. Research at UC Santa Barbara has slowed to a trickle to minimize person-to-person contact. “Our next steps, once research activities resume at UCSB, is to continue our work on improving our AlGaN/SiC platform to hopefully produce the world’s most efficient UVC light emitters,” he said.