Hybrid Integration of Tunnel-Junction InGaN/GaN and Wafer-Bonded AlGaInP/GaInP for Full-Color Micro-LEDs.

Area of Science:

• Materials Science
• Optoelectronics
• Display Technology

Background:

• Next-generation augmented and virtual reality (AR/VR) displays require extremely high pixel density and resolution.
• Monolithic 3D (M3D) integration of RGB micro-light-emitting diodes (micro-LEDs) offers a path to higher pixels per inch (PPI) than conventional lateral arrangements.
• Existing M3D integration methods involve complex multi-step processes like wafer-bonding and substrate removal.

Purpose of the Study:

• To develop a simplified hybrid wafer-bonding strategy for fabricating vertically integrated RGB micro-LED pixels.
• To achieve higher performance metrics (efficiency, color gamut) compared to existing M3D micro-LEDs.
• To enable scalable and efficient production of ultrahigh-resolution, full-color micro-LED displays for AR/VR applications.

Main Methods:

• A hybrid wafer-bonding strategy was developed, combining tunnel-junction-based blue-green micro-LED epitaxial layers with AlGaInP/GaInP red micro-LED epilayers.
• This architecture allows for vertical integration of RGB pixels using a single wafer-bonding step and removal of only one substrate.
• Fabrication focused on micro-LEDs with a pixel size of 30 × 30 μm².

Main Results:

• The hybrid M3D integration achieved record-high maximum external quantum efficiencies (EQEs): 5.8% (red), 15.7% (green), and 12.5% (blue).
• These efficiencies surpass those reported for previously developed M3D-stacked RGB micro-LEDs.
• The fabricated devices demonstrated full-color emission and achieved 95.7% coverage of the DCI-P3 color gamut.

Conclusions:

• The hybrid wafer-bonding strategy offers a simplified and efficient method for M3D integration of RGB micro-LEDs.
• This approach is a scalable route toward manufacturing ultrahigh-resolution, full-color micro-LED displays.
• The technology holds significant potential for advancing AR/VR display capabilities.