Acceptance cone coupling and pixel size dependence in micro-LEDs with surface domes

Abstract Micro-LED-on-silicon (LEDoS) light engines require emission within the finite angular acceptance cone of the downstream collection optics in display systems. We use cylindrical finite-difference time-domain simulations to evaluate sidewall inclination and hemispherical surface domes using cone-coupled efficiency. The reference pixel has a 2.0 µm active diameter and a 4.0 µm pitch, with a representative collection half-angle of 15°. Extraction through the pixel-cell area and cone-coupled efficiency favor different structures. A low-index dome improves angular coupling, but increasing the sidewall angle beyond approximately 30° provides limited additional angular benefit while increasing the minimum pitch required for mesa non-overlap. The dome response is non-monotonic with refractive index. In the size sweep, the angular benefit becomes negligible at an active diameter of 1 µm, although a small extraction-related efficiency gain remains. These results connect pixel-level optical design to the collection requirements and geometric constraints of LEDoS light engines, within the tested dome geometry and source conditions.