Operating behavior of micro-LEDs on a GaN substrate at ultrahigh injection current densities.

Area of Science:

• Solid State Physics
• Optoelectronics
• Materials Science

Background:

• Micro-light-emitting diodes (micro-LEDs) are crucial for advanced display and lighting technologies.
• Understanding carrier transport and recombination mechanisms in micro-LEDs at high current densities is essential for performance optimization.

Purpose of the Study:

• To investigate the electrical and optical characteristics of near-ultraviolet (NUV) micro-LEDs fabricated on Gallium Nitride (GaN) substrates.
• To analyze carrier transport and recombination dynamics under high injection current densities.

Main Methods:

• Fabrication of NUV micro-LEDs with varying diameters on GaN substrates.
• Measurement of electroluminescence, light output power-current density, and current density-voltage characteristics.
• Simulation of micro-LED transport and recombination processes using an integrated quantum drift-diffusion model, incorporating many-body effects and phase space filling.

Main Results:

• Achieved a saturated current density of 358 kA/cm² for a 20 µm diameter micro-LED.
• Observed stepped and peaked ideality factor curves with abnormal efficiency increases between 20 and 150 kA/cm².
• Identified significant current crowding above 100 kA/cm², even in the 20 µm device.

Conclusions:

• High current densities are achievable in NUV micro-LEDs, but performance is limited by carrier transport phenomena.
• The integrated quantum drift-diffusion model effectively captures the complex behavior of micro-LEDs at high injection levels.
• Current crowding is a critical factor affecting the efficiency and performance of micro-LEDs at high operating currents.