Enhanced and directional electroluminescence from MicroLEDs using metallic or dielectric metasurfaces.

Abstract

Micro light-emitting diode devices (microLEDs) have the potential to lead the next generation of displays. However, their integration for achieving high brightness is severely limited by the challenge of their low external quantum efficiency (EQE). Another limiting factor of such devices is their Lambertian emission, which requires secondary optics to beam the emitted light in defined directions. To address these limitations, we introduce metallic and dielectric metasurfaces to improve light outcoupling efficiency and control the emission directionality of blue LEDs with micrometer size. The proposed mechanism relies on the interaction between light emitted by multiple quantum wells (MQWs) and metasurfaces supporting collective resonances that result from the coupling of localized resonances in nanoparticles throughout the array. We implemented a hexagonal diffraction lattice of resonant Al and SiO₂ nanoparticles in LED devices to achieve reshaping of the far-field electroluminescence, thus demonstrating light beam control capabilities on these emitters. To expand and validate the proposed approach for small LED devices (even at the sub-micrometer scale), we integrate a subdiffraction lattice of Al nanoparticles into the device's architecture. Implementing the proposed design allows us to control the generated light and achieve enhanced far-field emission.