The Origin of Efficiency in III-Nitride Micro-Light-Emitting Diodes

Area of Science:

• Materials Science
• Optoelectronics
• Semiconductor Physics

Background:

• Micro-light-emitting diodes (µLEDs) are crucial for advanced display and lighting technologies.
• Indium Gallium Nitride (InGaN) materials are widely used in µLED fabrication, but their efficiency is limited by various factors.
• Understanding the factors affecting external quantum efficiency (EQE) is vital for optimizing µLED performance.

Purpose of the Study:

• To investigate the primary factors influencing the external quantum efficiency (EQE) of InGaN-based µLEDs.
• To compare the carrier diffusion lengths and the impact of sidewall conditions on red and blue InGaN µLEDs.
• To determine the relationship between peak wavelength, internal material properties, and EQE in InGaN red µLEDs.

Main Methods:

• Comparative photoluminescence (PL) studies were conducted on InGaN red and blue µLEDs.
• Lateral carrier diffusion lengths were measured and analyzed.
• Examinations of EQE and peak wavelength were performed across varied epitaxial designs and sidewall conditions.
• Statistical analysis using relative standard deviation was employed to identify key determinants of EQE.

Main Results:

• Lateral carrier diffusion length in InGaN red µLEDs is significantly shorter than in blue InGaN µLEDs due to bulk material inhomogeneity.
• Sidewall-surface recombination has a negligible impact on the EQE of InGaN red µLEDs.
• The peak wavelength, reflecting radiative recombination rate, dominantly influences the EQE of InGaN red µLEDs.
• Peak wavelength is identified as a primary determinant of EQE in InGaN red µLEDs.

Conclusions:

• The internal state of InGaN-based µLEDs is the principal factor governing their EQE.
• Optimizing the internal material properties and quantum well design is critical for enhancing µLED performance.
• Focusing on internal state optimization, particularly peak wavelength control, is essential for improving InGaN red µLED EQE.