Effect of n-type AlGaN buffer layers Growth Temperature on relaxation and conductivity in 228-230nm Far-UVC LED grown on c-Sapphire

The increasing resistance of Methicillin-Resistant Staphylococcus Aureus (MRSA) to antibiotics is a major challenge faced by mankind in the history of medical science. Aluminum gallium nitride (AlGaN) based 228-230 nm-band Far-ultraviolet-C (Far-UVC) light sources can be used as a germicidal application in both manned as well as in unmanned environments against these MROs including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Because Far-UVC spectra < 230nm cannot penetrate the human skin cells, and eyes too and it can be only absorbed by the outermost hard protein layer (keratin) of the skin before it could reach the underlying living cells. Previously, the Far-UVC LED with emission power of 1.7 mW and EQE of 0.32% at peak wavelength of 228nm was reported, however the n-AlGaN buffer layer was not optimized. In this work, the influence of n-AlGaN buffer layer`s growth temperature on its relaxation and electrical properties in 228 -230nm Far-UVC LED grown on c-Sapphire is attempted using a special growth technique in SR4000-MOCVD reactor to control the conductivity as well as relaxation in the n-AlGaN buffer layer. The low relaxation ratio is critical for the suppression of transvers magnetic (TM)-mode as well as for promoting transverse electric (TE)-mode emission (along c-axis). In our previous work, relatively high operating voltages of approximately ~ 30 V at 20 mA using thick Ni (20nm)/Au (100nm) p-electrode were observed. Finally, such issue of high operating voltage was overcome using optimized growth condition and the relaxation ratio was reduced from 41.6% to 20% successfully. As a result, the power and EQE were significantly improved to 2.2 mW and 0.40% under pulse-operation as well as 1.4 mW and 0.34% under CW-operation at RT. Finally, relatively low operating voltages of approximately ~ 24 V at 20 mA using thick Ni (20nm)/Au (100nm) p-electrode in 230nm Far-UVC LED were realized.