Superior current spreading in InGaN green micro-LEDs achieved by hexagonal mesa engineering

To address the challenge of low external quantum efficiency (EQE) in green micro-light-emitting diodes (micro-LEDs), we systematically investigated the effects of circular, square, and hexagonal mesa geometries. Through comprehensive fabrication and characterization, we demonstrate that the hexagonal mesa geometry significantly enhances device performance, achieving an optical output power density of 4.94 W/cm² at 200 A/cm², representing 1.57-fold and 1.28-fold enhancements compared to the square and circular configurations, respectively. Furthermore, it exhibits the lowest efficiency droop ratio among the geometries, and its peak EQE represents 1.18-fold and 1.13-fold enhancements compared to the circular and square configurations. These improvements are attributable to a minimized perimeter-to-emission area ratio that effectively suppresses Shockley-Read-Hall non-radiative recombination, and improved current spreading resulting from the reduced distance from the electrode edge to the mesa edge. These findings underscore the effectiveness of geometric optimization in significantly enhancing the optoelectronic performance of InGaN-based green micro-LEDs, providing a feasible strategy to achieve uniform current spreading and high quantum efficiency in micro-LEDs for integrated pixel architectures.