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

For next-generation augmented and virtual reality (AR/VR) displays, which demand extremely high pixel density and resolution, monolithic 3D (M3D) integration of RGB micro-LED pixels is regarded as a promising approach for achieving higher pixels per inch (PPI) than conventional lateral pixel arrangements. To circumvent the highly complex processes involving multiple wafer-bonding and substrate-removal steps, we developed a hybrid wafer-bonding strategy that combines tunnel-junction-based blue-green micro-LED epitaxial layers with AlGaInP/GaInP red micro-LED epilayers. This hybrid architecture enables the fabrication of vertically integrated RGB pixels using only a single wafer-bonding step and removal of one substrate. The stacked devices exhibited record-high maximum external quantum efficiencies (EQEs) of 5.8% for red, 15.7% for green, and 12.5% for blue at a pixel size of 30 × 30 μm², surpassing previously reported M3D-stacked RGB micro-LEDs. Full-color emission was confirmed by optical microscope imaging, and the devices demonstrated 95.7% coverage of the DCI-P3 color gamut. These results highlight the potential of hybrid M3D integration as a scalable and efficient route toward ultrahigh-resolution, full-color micro-LED displays for future AR/VR systems.