Suppressing sidewall photon leakage in ultra-small Micro-LEDs via omnidirectional reflector integration

We report the integration of an omnidirectional reflector (ODR) into GaN-based Micro-LEDs to enhance photon management and external quantum efficiency (EQE) in ultra-small devices. Conventional distributed Bragg reflectors (DBRs) suffer performance loss under sidewall thickness variation and oblique photon incidence, limiting light extraction in micrometer-scale Micro-LEDs. In contrast, simulations show that ODRs maintain high reflectance under both sidewall thickness variation and wide-angle incidence, efficiently redirecting photons toward the designated surface. Experimentally, a Micro-LED with a 2 μm lateral size achieves a peak EQE of 42.3% after ODR integration, compared with approximately 25.6% for the device without an optical reflector. This corresponds to an absolute increase of about 16%, or a relative improvement of 67%. Meanwhile, the ODR-integrated devices maintain stable electrical characteristics and exhibit enhanced EQE across a broad current density range. These results establish ODR integration as a scalable and practical strategy for efficient photon extraction in GaN-based ultra-small Micro-LEDs, with direct implications for high-resolution micro-display applications.