High-Resolution Visualization of Sidewall Defects in Gallium Nitride Micro LEDs

A team of researchers from Xiamen University has made a breakthrough in the development of gallium nitride (GaN) micro light-emitting diodes (Micro LEDs). Using a multi-physical field microscopic imaging system, they have successfully localized and characterized defects in these micro LEDs, which is crucial for optimizing their performance. The study demonstrates the potential of wet etching in mitigating plasma etching-induced damages, leading to enhanced brightness and external quantum efficiency.

Key Takeaways:

• The researchers developed a multi-physical field microscopic imaging system that enables high spatiotemporal resolution characterization of individual GaN Micro LEDs.
• The system integrates fluorescence imaging, fluorescence lifetime imaging microscopy, hyperspectral imaging, and time-correlated single-photon counting to track the evolution of defects under coupled optical, electrical, and thermal fields.
• The study revealed two distinct regions of defects near the chip edges: a narrow fluorescence lifetime decrease zone (approximately 2 μm) and a broader fluorescence intensity decrease zone (approximately 5 μm).
• The researchers proposed a physical model that describes the interplay between defect-induced non-radiative recombination and carrier diffusion.
• Wet etching was found to effectively mitigate ICP-induced damages, leading to enhanced brightness and external quantum efficiency.
• The passivation process enabled a 3 μm size blue Micro LED chip to achieve a peak external quantum efficiency of 27.6% with a current density of 33.7 A/cm².

Statistics:

• The multi-physical field microscopic imaging system achieved high spatiotemporal resolution characterization of individual GaN Micro LEDs.
• The system enabled real-time tracking of the evolution of defects under coupled optical, electrical, and thermal fields.
• The study revealed that wet etching effectively mitigated ICP-induced damages, leading to enhanced brightness across a range of Micro LED sizes.
• The passivation process enabled a 27.6% peak external quantum efficiency with a current density of 33.7 A/cm² in a 3 μm size blue Micro LED chip.

Sources:

• "High-resolution Visualization of Sidewall Defects In Gallium Nitride Micro Light-emitting Diode Via Multi-physical Field Luminescence Imaging Microscopy." Applied Physics Letters, 2025;127(12).
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• American Institute of Physics - www.aip.org/; Applied Physics Letters - apl.aip.org/
• Jinchai Li, Xiamen University, Dept. of Physics, Fujian Key Laboratory of Semiconductor Materials and Applications, Xiamen 361005, People's Republic of China.