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Beam divergence measurements of InGaN/GaN micro-array light-emitting diodes using confocal microscopy

Griffin, C. and Gu, E. and Choi, H.W. and Jeon, C.W. and Girkin, J.M. and Dawson, M.D. and McConnell, G. (2005) Beam divergence measurements of InGaN/GaN micro-array light-emitting diodes using confocal microscopy. Applied Physics Letters, 86 (4). ISSN 0003-6951

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The recent development of high-density, two-dimensional arrays of micrometer-sized InGaN/GaN light-emitting diodes (micro-LEDs) with potential applications from scientific instrumentation to microdisplays has created an urgent need for controlled manipulation of the light output from these devices. With directed light output these devices can be used in situations where collimated beams or light focused onto several thousand matrix points is desired. In order to do this effectively, the emission characteristics of the devices must be fully understood and characterized. Here we utilize confocal microscopy to directly determine the emission characteristics and angular beam divergences from the individual micro-LED elements. The technique is applied to both top (into air) and bottom (through substrate) emission in arrays of green (540 nm), blue (470 nm), and UV (370 nm) micro-LED devices, at distances of up to 50 µm from the emission plane. The results are consistent with simple optical modeling of the expected beam profiles.