Tunnelling junction enhances deep UV LEDs
Chinese team achieve lowest operating voltage for deep UV LEDs and enable disinfection and water/air purification
Researchers from Wuhan University and Ningbo ANN Semiconductor in China have made significant progress in improving optoelectronic performance for deep ultraviolet (UV) LEDs.
“We propose the implementation of an ultrathin tunnelling junction (UTJ) technology platform in deep-UV LEDs as a solution to the challenges of high series resistance and deep-UV light absorption. In our study, we successfully develop 275 nm high-power UTJ deep-UV LEDs, achieving the lowest voltage of 5.7 V to date, which is enabled by minimizing electrical losses for hole injection.” said Shengjun Zhou, a professor at Wuhan University who directed the research.
The intriguing properties of deep UV light and its potential applications make it an attracting subject for fundamental studies. The wavelength range of deep-UV (200-280 nm) has been found to be highly effective in sterilisation and disinfection by damaging the DNA and RNA of bacteria and viruses. However, the low light output power and high operating voltage of deep-UV LEDs make it difficult for current LEDs integrated deep-UV light sources to meet the sterilisation performance targets of effective irradiation distance and exposure time.
To address these issues, the researchers from Wuhan University proposed to introduce the UTJ as a direct contact layer in deep-UV LEDs for minimising the electrical losses. The schematic illustration above shows the deep-UV LED epitaxial structure grown on AlN/Flat Sapphire Substrate template
They observed the formation of Mg-Si co-doped n-AlGaN during the high-temperature growth of UTJ and discovered that the UTJ can form Ohmic contact with the high-work-function Ni/Au electrode. Furthermore, the encapsulation of UTJ deep-UV LED with Zener diode, fluorine resin, and optimally designed glass lens was demonstrated to improve the reliability and optical performance.
They developed a high-efficiency sterilisation deep-UV light source integrated with 120 UTJ deep-UV LED chips and conducted the experiments on the killing effect of deep-UV light source on multiple pathogenic microorganisms and flowing water sterilisation.
Zhou and colleagues say that the findings are significant and have the potential to enhance the utilisation of deep-UV light sources for water/air purification and disinfection.
'High-Power AlGaN-Based Ultrathin Tunneling Junction Deep Ultraviolet Light-Emitting Diodes' by Shengjun Zhou et al; Laser & Photonics Reviews, 2023