Epitaxial Light Control Features in Light Emitting Diodes

Background

Increasing internal quantum efficiency (IQE) and light extraction efficiency (EXE) are the two main approaches to improving the overall efficiency of LEDs. EXE can be increased by improving the directionality of light emission, and the introduction of photonic crystals (PhCs) to LEDs provided a promising advancement toward this goal. However the delicate fabrication requirements of PhC LEDs keeps them from realizing large scale production. A solution that circumvents this delicate fabrication process would enable widespread implementation of PhC LEDs and usher in a significant increase to the overall efficiency of LEDs.

Description

Researchers at the University of California, Santa Barbara have developed highly efficient PhC LEDs of micro and macro size (100000 µm2 to 1 µm2) with epitaxially integrated light control features. As a departure from conventional PhC LED fabrication, this invention does not etch directly on the active layer, which eliminates possible damage to the quantum wells (QW). Instead, light-controlling structures are epitaxially integrated directly onto the device layer at the initial stage of growth. The epitaxial layers are defect-filtered through epitaxial lateral overgrowth (ELO), providing controlled light extraction and directionality and improving EXE. This technology integrates PhCs on the n-GaN side of micro-LEDs which also addresses the color mixing issues of burgeoning high pixel density micro-displays. Micro-displays that demonstrate these performance features will represent the future of AR/VR/Mixed reality applications where light directionality is crucial.

Advantages

• Improved efficiency through optimized light extraction and directionality
• Avoids damage caused by physical etching on the active layer
• Decreased defect density
• Can be used with native or foreign substrates regardless of crystal orientation

Applications

• LEDs and micro-LEDs
• AR/VR
• Next generation displays

Patent Status