Thermophysical Characterization of Efficiency Droop in GaN-Based Light-Emitting Diodes

Area of Science:

• Solid State Physics
• Materials Science
• Optoelectronics

Background:

• Efficiency droop in light-emitting diodes (LEDs) is a significant challenge impacting performance.
• Indium gallium nitride/gallium nitride (InGaN/GaN) heterobarrier structures are employed to mitigate emission degradation.

Purpose of the Study:

• To characterize the efficiency droop in GaN-based LEDs using thermophysical parameters.
• To investigate the relationship between heterobarrier structures, Debye temperature, electron-phonon interaction, and efficiency droop.
• To establish a thermophysical marker for assessing LED performance and guiding heterodevice optimization.

Main Methods:

• Temperature-dependent current-voltage measurements of InGaN/GaN multiple-quantum-well LEDs from 20 to 300 K.
• Analysis of Debye temperatures and electron-phonon interaction coupling coefficients.
• Calculation of the Debye temperature to coupling coefficient ratio (DCR) as a performance indicator.

Main Results:

• Debye temperature of LEDs is influenced by the InN molar fraction in heterobarriers.
• Electron-phonon interaction coupling coefficients correlate with non-radiative transition rates.
• The DCR was found to be directly correlated with quantum efficiency (QE).
• High/low DCR values corresponded to high/low QEs at low/high injection currents, respectively.

Conclusions:

• The DCR serves as a reliable thermophysical marker for characterizing LED efficiency droop.
• The DCR can be utilized for optimizing heterodevice structures to enhance LED performance.
• Understanding electron-phonon interactions and Debye temperature is crucial for mitigating efficiency droop in InGaN/GaN LEDs.