Flip-chip InGaN light-emitting diodes with an integrated microlens array

The fabrication of hexagonally close-packed lens array on flip-chip bonded InGaN LED by nanosphere lithography is reported. A self-assembled monolayer of silica spheres with diameters of 1-μm serves as an etch mask to be transferred onto the sapphire face of the LED to form hemispherical lenses. Without degrading electrical characteristic, the light output power of lensed LED is increased by more than one-quart, compared with an unpatterned LED. The optical behavior of individual lenses and converging effect of lensed LED are by ray-tracing and confocal imaging.