Enhanced light extraction efficiency of GaN-based green micro-LED modulating by a thickness-tunable SiO₂ passivation...

Area of Science:

• Optoelectronics
• Materials Science
• Semiconductor Devices

Background:

• Green micro-light emitting diodes (micro-LEDs) are crucial for full-color displays.
• Decreasing micro-LED size exacerbates sidewall damage during inductively coupled plasma (ICP) etching.
• Silicon dioxide (SiO2) passivation is a key strategy to mitigate etching-induced damage.

Purpose of the Study:

• To investigate the impact of SiO2 passivation layer thickness on green micro-LED performance.
• To optimize SiO2 passivation for improved light extraction efficiency (LEE) and device reliability.
• To validate simulation predictions through experimental fabrication and characterization.

Main Methods:

• Finite-difference time-domain (FDTD) simulations were used to design green rectangular micro-LEDs with varying SiO2 passivation thicknesses (0–600 nm).
• Micro-LED arrays were fabricated using high-speed, large-area parallel laser micro-lens array (MLA) lithography.
• The performance of micro-LEDs with different SiO2 passivation thicknesses was experimentally analyzed.

Main Results:

• The light extraction efficiency (LEE) showed a periodic fluctuation with increasing SiO2 passivation layer thickness.
• A SiO2 passivation layer of 90 nm resulted in minimal leakage current and higher operating current density.
• The maximum external quantum efficiency (EQE) achieved was 2.8 times greater compared to micro-LEDs without SiO2 passivation.

Conclusions:

• SiO2 passivation is an effective method for reducing sidewall damage and enhancing the performance of green micro-LEDs.
• Optimizing SiO2 passivation thickness is critical for maximizing EQE and device performance.
• The study demonstrates a viable approach for fabricating high-performance micro-LEDs through simulation and experimental validation.