Distinct U-shape efficiency-versus-current curves in AlGaN-based deep-ultraviolet light-emitting diodes

Area of Science:

• Optoelectronics
• Semiconductor Physics
• Materials Science

Background:

• Deep-ultraviolet light-emitting diodes (DUV LEDs) are crucial for applications like sterilization and sensing.
• Understanding efficiency limitations in AlGaN-based DUV LEDs is vital for performance optimization.
• Previous studies often focused on room-temperature characteristics, leaving low-temperature behavior less explored.

Purpose of the Study:

• To investigate the efficiency-current relationship of an AlGaN DUV LED at various temperatures (110 K to 300 K).
• To elucidate the underlying physical mechanisms responsible for observed efficiency variations, particularly at low temperatures and high current densities.

Main Methods:

• Experimental characterization of an AlGaN DUV LED (peak emission 285 nm).
• Measurement of electroluminescence efficiency as a function of injection current across a wide temperature range.
• Differential conductivity measurements to probe carrier transport properties.

Main Results:

• The efficiency-current curves displayed unique features, including three inflection points across all tested temperatures.
• At low temperatures, a distinct efficiency minimum was observed after which efficiency increased with current.
• High-current density operation at low temperatures resulted in higher efficiency than at room temperature.

Conclusions:

• The observed efficiency behavior, especially the low-temperature minimum, is attributed to field-ionization of acceptors enhancing p-type conductivity in the high-injection regime.
• Differential conductivity measurements confirmed a significant rise in the high-injection regime, correlating with the efficiency minimum.
• These findings provide critical insights into the operational physics of AlGaN DUV LEDs and suggest pathways for improved device design.