Analysis of micro-lens integrated flip-chip InGaN light-emitting diodes by confocal microscopy

– KH Li, C Feng, and HW Choi

Schematic diagram depicting the flip-chip LED with a micro-lens array on the sapphire surface; (b) AFM and (c) SEM images showing the hemispherical lens array.

Applied Physics Letters, vol. 104, 5, pp. 051107 (2014)

A hexagonally close-packed microlens array has been integrated onto the sapphire face of a flip-chip bonded InGaN light-emitting diode (LED). The micro-optics is formed by etching a self-assembled monolayer of 1-μm silica microspheres coated on the sapphire substrate, producing hemispherical sapphire lenses. Without degrading electrical characteristic, the light output power of the lensed LED is increased by more than a quarter compared with the unlensed LED. Enhanced light extraction via micro-optics is verified by rigorous coupled wave analysis. The focusing behavior of the micro-lenses, as well as the emission characteristics of the lensed LED, is studied by confocal microscopy.

DOI: 10.1063/1.4863925