Suppressing the efficiency droop in the AlGaN-based UVB LED.

Optoelectronic properties of semiconducting aluminum gallium nitride (AlGaN) - based ultraviolet - B (UVB) light-emitting diodes (LEDs) are crucial for the real-world medical applications such as cancer and immunotherapy. Therefore, we have numerically investigated the performances of AlGaN-based UVB LEDs for the suppression of efficiency droop as well as for the enhancement of hole injection in the multiquantum wells (MQWs). The influence of the undoped (ud)-AlGaN final barrier (FB) as well as Mg-doped multiquantum barrier electron blocking layer (p-MQB EBL) on the efficiency droop has been specifically focused. For the evaluation of the proposed device performance, we have compared its internal quantum efficiency (IQE), carrier concentration, energy band diagram, and radiative recombination rate with the conventional device structure. Furthermore, the influence of Al-composition in the p-AlGaN hole source layer (HSL) on the operating voltages of the proposed UVB LEDs was considered. The simulation results suggest that our proposed structure has high peak efficiency and much lower efficiency droop as compared to the reference structure (conventional). Ultimately, the radiative recombination rate in the MQWs of the proposed structure has been found to raise up to ~73%, which is attributed to the enhanced level of electron and hole concentrations by ~64% and 13% , respectively, in the active region. Finally, a high efficiency droop up to ~42% in RLED has been found successfully suppressed to ~7% by using optimized ud-AlGaN FB and p-MQB EBL in the proposed UVB device structure.