Suppressing the efficiency droop in the AlGaN-based UVB LED

Area of Science:

• Optoelectronics and semiconductor physics.
• Materials science of nitride semiconductors.
• Photonics and device engineering.

Background:

• Aluminum gallium nitride (AlGaN)-based ultraviolet-B (UVB) light-emitting diodes (LEDs) are vital for medical applications like cancer therapy and immunotherapy.
• Efficiency droop and poor hole injection in UVB LEDs limit their practical performance.
• Understanding and mitigating these issues are critical for advancing UVB LED technology.

Purpose of the Study:

• To numerically investigate AlGaN-based UVB LEDs for efficiency droop suppression and enhanced hole injection.
• To analyze the impact of an undoped (ud)-AlGaN final barrier (FB) and a Mg-doped multiquantum barrier electron blocking layer (p-MQB EBL).
• To evaluate the influence of Al-composition in the p-AlGaN hole source layer (HSL) on operating voltages.

Main Methods:

• Numerical simulations were employed to model and compare device performance.
• Key performance metrics including internal quantum efficiency (IQE), carrier concentration, energy band diagrams, and radiative recombination rates were evaluated.
• The proposed device structure was compared against a conventional reference structure.

Main Results:

• The proposed UVB LED structure demonstrated significantly lower efficiency droop (7% vs. 42%) compared to the conventional structure.
• A substantial increase in the radiative recombination rate within the multiquantum wells (MQWs) by up to ~73% was observed.
• Electron and hole concentrations in the active region were enhanced by ~64% and ~13%, respectively.

Conclusions:

• The optimized structure, incorporating ud-AlGaN FB and p-MQB EBL, effectively suppresses efficiency droop in AlGaN-based UVB LEDs.
• Enhanced carrier concentrations and radiative recombination rates contribute to improved device performance.
• The findings pave the way for more efficient UVB LEDs for critical medical applications.