Optical characteristics of thin film-based InGaN micro-LED arrays: a study on size effect and far field behavior

Area of Science:

• Optoelectronics and Photonics
• Materials Science
• Semiconductor Devices

Background:

• Micro-light emitting diodes (µ-LEDs) are crucial for high-resolution displays in augmented reality, smartphones, and head-up displays.
• Thin-film chip architectures are essential for fabricating µ-LEDs with sub-micrometer pixel sizes.

Purpose of the Study:

• To fabricate and characterize nitride-based µ-LED arrays with lateral pixel sizes down to 1 µm.
• To investigate the impact of pixel size on light extraction efficiency (LEE) and far-field properties.
• To analyze the influence of dielectric layer thickness on µ-LED optical performance.

Main Methods:

• Fabrication of nitride-based µ-LED arrays using thin-film chip architecture.
• Electro-optical characterization of µ-LEDs (1x1 to 8x8 µm²) using an integrating sphere and goniometer.
• Finite-difference time-domain (FDTD) simulations to model wave optical effects.

Main Results:

• External quantum efficiencies increase with decreasing µ-LED size, attributed to enhanced light extraction efficiency (LEE).
• Far-field properties exhibit significant changes with varying pixel sizes.
• Aluminium oxide layer thickness variations (40 nm vs. 80 nm) lead to distinct far-field patterns, highlighting sensitivity to design.

Conclusions:

• Wave optical effects significantly impact µ-LED performance, necessitating detailed modeling.
• Understanding and simulating these effects are critical for optimizing µ-LED design and achieving desired optical properties.
• The study demonstrates the feasibility of fabricating high-performance µ-LEDs for advanced display applications.