Enhanced forward emission by backside mirror design in micron-sized LEDs

Area of Science:

• Optoelectronics
• Materials Science
• Nanotechnology

Background:

• Indium gallium nitride (InGaN) micro-light-emitting diodes (μ-LEDs) are crucial for advanced display technologies like augmented reality (AR).
• High internal quantum efficiency (IQE) and light extraction efficiency (LEE) are critical for μ-LED performance.
• Traditional methods like wet chemical etching to restore IQE after dry etching negatively impact pixel shape and LEE.

Purpose of the Study:

• To overcome the limitations of existing μ-LED fabrication methods.
• To enhance the light extraction efficiency (LEE) of InGaN μ-LEDs without compromising pixel shape.
• To improve the performance of μ-LEDs for projection display applications.

Main Methods:

• Fabrication of 1 μm thin-film-based μ-LED emitter arrays.
• Integration of a metallic backside mirror on a patterned dielectric material surrounding the μ-LED mesa.
• Utilizing a concave mirror design to redirect photons within the μ-LED structure.

Main Results:

• Demonstrated a straightforward integration of the concave mirror into a thin-film LED process.
• Achieved enhanced LEE by redirecting photons within the μ-LED structure.
• Observed a 2.1-fold improvement in light output within the ±15° emission cone compared to μ-LEDs with vertical sidewalls.

Conclusions:

• The developed concave metallic backside mirror effectively enhances LEE in InGaN μ-LEDs.
• This method offers a significant improvement for μ-LED projection displays by boosting efficiency and directionality.
• The findings pave the way for more efficient and high-performance micro-display technologies.