7 December 2013 Fabrication and replication of micro-optical structures for growth of GaN-based light emitting diodes
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GaN light emitting diodes (LEDs) on sapphire substrates can be improved by micro-patterning substrate to perform epitaxial over-growth which drastically reduces defects' density in the light emitting region. We patterned Al2O3 with focused ion beam and show a successful overgrowth of GaN. The exact shape of pattern milled into Al2O3 was replicated into a 0.4-mm-thick shim of Ni by electroplating. The surface roughness of Ni was ~5:5 ±2 nm and is applicable for the most demanding replication of nano-rough surfaces. This technique can be used to replicate at micro-optical elements Fresnel-axicons defined by electron beam lithography made on sub-1 mm areas without stitching errors (Raith EBL). Shimming of macro-optical elements such as car back- reflectors is also demonstrated. Ni-shimming opens possibility to make replicas of nano-textured small and large area patterns and use them for thermal embossing and molding of optically-functionalized micro-fluidic chips and macro-optical elements.
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G. Gervinskas, G. Gervinskas, G. Seniutinas, G. Seniutinas, A. Vijayakumar, A. Vijayakumar, S. Bhattacharya, S. Bhattacharya, E. Jelmakas, E. Jelmakas, A. Kadys, A. Kadys, R. Tomašiūnas, R. Tomašiūnas, S. Juodkazis, S. Juodkazis, "Fabrication and replication of micro-optical structures for growth of GaN-based light emitting diodes", Proc. SPIE 8923, Micro/Nano Materials, Devices, and Systems, 89234L (7 December 2013); doi: 10.1117/12.2033709; https://doi.org/10.1117/12.2033709

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