A Korean research team has developed a deep-ultraviolet (DUV) LED with an entirely new material. The DUV LED refers to a semi­conductor light source designed to emit ultraviolet (UV) light with a short wavelength of 200 to 280 nanometers. Irradiating this LED on viruses or bacteria destroys harmful pathogens while mini­mizing harm to the human body. A Postech research team led by Jonghwan Kim, Su-Beom Song and Sangho Yoon has produced DUV LED for the first time using hexagonal boron nitride (hBN).

UV light can destroy or alter the form of a material. Among UV lights, the near-UV light has high penetration depth and can cause diseases when the skin is exposed to it. However, DUV light has extremely low skin pene­trability and is anticipated to be safely used. For this reason, research to develop DUV LEDs has been active, mainly using aluminum gallium nitride. However, this material has a funda­mental limitation in that its electro­luminescence rapidly deteriorates as the wavelength becomes shorter and fabricating LEDs that can be used in the DUV frequencies remains a challenge.

Hexagonal boron nitride (hBN) used by Jonghwan Kim's research team is a van der Waals layered material like graphite. Its monolayer structure is similar to graphene and is transparent. Unlike aluminum gallium nitride, it emits luminescence at DUV fre­quencies and therefore considered an effective new material for developing DUV LEDs. However, it has been difficult to inject electrons and holes due to its large bandgap, rendering it difficult to make into an LED. To this, the researchers focused on injecting electrons and holes to the hBN band edges by applying a strong voltage to the hBN nanofilm inducing the tunneling mechanism. With this, the researchers success­fully fabricated an LED device based on a van der Waals hetero­structure stacked with graphene, hBN, and graphene. Subsequent DUV micro-spectro­scopy confirmed that the newly fabricated device emits strong UV light.

“The development of a new high-efficiency LED material in a new frequency can be the starting point for pioneering ground­breaking optical device appli­cations that have never been seen before,” remarked Professor Jonghwan Kim who led the study. “It is signi­ficant that this study presented the first demons­tration of a deep-ultraviolet LED based on hBN.” He added, “Compared to the conven­tional aluminum gallium nitride material, the new material has significantly higher efficiency of luminescence and enables miniaturi­zation. It is anti­cipated to be highly applicable in viral and bacterial sterilization systems, semi­conductor device manu­facturing processes, and short-range wireless communi­cation in the future.” (Source: Postech)

Reference: S.-B. Song et al.: Deep-ultraviolet electroluminescence and photocurrent generation in graphene/hBN/graphene heterostructures, Nat. Commun. 12, 7134 (2021); DOI: 10.1038/s41467-021-27524-w

Link: Dept. of Materials Science and Engineering, Pohang University of Science and Technology Postech, Pohang, Republic of Korea