12 March 2020
University of California Santa Barbara (UCSB) in the USA has been using silicon carbide (SiC) substrates to grow aluminium gallium nitride (AlGaN) structures aimed at 278nm deep ultraviolet (UV-C, 100-280nm wavelength) light-emitting diodes (LEDs) [Burhan K. SaifAddin et al, ACS Photonics, published online 27 January 2020]. TSehe researchers used surface roughening of thin-film flip-chip devices to boost light-extraction efficiency (LEE) by a factor of 3 over smooth-faced LEDs.
“The ability to grow AlGaN LEDs on SiC with low TDD [threading dislocation density] opens new ways to fabricate high-brightness, high-power UV LEDs with high LEE,” the team comments. The 260-280nm wavelength range enables efficient disinfection by breaking up DNA and RNA molecules of pathogens. The researchers are keen to combat antibiotic-resistant bacteria such as Clostridium difficile (C. diff.), which is indeed difficult to kill using chemical methods. By contrast, UV disinfection reduced C. diff. levels by 30%, according to University of North Carolina researchers in 2010.