Achieving zero efficiency droop in highly efficient N-polar AlGaN tunnel junction-based 254 nm DUV LED

The Minamata Convention of 2020 mandates the replacement of conventional mercury UV lamps with deep ultraviolet (DUV) light-emitting diodes (LEDs) emitting at 254 nm. But both the traditional DUV LEDs (C-LEDs) and tunnel junction (TJ)-based UVC LEDs face challenges such as high operating voltages and inefficient hole injection. Utilizing p-AlGaN and n-AlGaN layers-based TJ in DUV LEDs shows promise in addressing these issues, particularly in mitigating contact resistance and improving hole injection efficiency at the 254 nm emission wavelength. This study presents an approach to manipulate quantum tunnelling probability in n-AlGaN/p-AlGaN tunnel junctions by optimizing doping levels and thickness using APSYS Software simulations. The result is a suppression of Auger recombination and increased radiative recombination rates in 254 nm TJ-based DUV LEDs compared to C-LED. Theoretical modeling shows an internal quantum efficiency (IQE) of approximately 88 % with zero efficiency droop in TJ-based LEDs, a significant improvement over the approximately 66 % IQE with a 53 % efficiency droop in C-LEDs. This study reveals the highest theoretically possible IQE of 88 % at a 254 nm emission wavelength in TJ-based LED, with no efficiency droop. Moreover, TJ-LEDs show linear increases in light output powers (LOP) with varying current densities due to lower Auger recombination rates in their multiquantum wells (MQWs). Notably, operating voltages reduce significantly from 21 V to 5.4 V under 200 A/ cm2 operation, attributed to optimized TJ thickness and doping, along with a careful selection of lower Alcontent in the contact layer. These findings pave the way for enhanced UV emitter growth using techniques like metal-organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE), promising advancements in biomedical applications.