Suppressing the efficiency droop in AlGaN-based UVB LEDs

Area of Science:

• Optoelectronics
• Semiconductor Physics
• Materials Science

Background:

• Aluminum gallium nitride (AlGaN)-based ultraviolet-B (UVB) light-emitting diodes (LEDs) are vital for medical applications.
• Current UVB LED performance is limited by poor hole injection efficiency and efficiency droop.

Purpose of the Study:

• To numerically investigate AlGaN-based UVB LEDs for improved performance.
• To suppress efficiency droop and enhance hole injection in multiquantum wells (MQWs).

Main Methods:

• Numerical investigation of AlGaN-based UVB LED structures.
• Focus on the influence of undoped (ud)-AlGaN final quantum barrier (FQB) and Mg-doped multiquantum barrier electron blocking layer (p-MQB EBL).
• Evaluation of internal quantum efficiency (IQE), carrier concentration, energy band diagram, and radiative recombination rate.

Main Results:

• The proposed structure shows higher peak efficiency and significantly lower efficiency droop compared to conventional structures.
• Radiative recombination rate in MQWs increased by approximately 73%.
• Electron and hole concentrations in the active region enhanced by approximately 64% and 13%, respectively.

Conclusions:

• Optimized ud-AlGaN FQB, p-MQB EBL, and Al-graded p-AlGaN hole source layer (HSL) effectively suppress efficiency droop.
• The proposed UVB LED-N structure demonstrates a substantial reduction in efficiency droop from ~42% to ~7%.
• Enhanced carrier concentrations lead to improved radiative recombination and overall device performance for medical applications.