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Proceedings Paper

Photonic crystal based control of directionality in GaN based LEDs
Author(s): Thomas M. Mercier; Chirenjeevi Krishnan; Peter J. Shaw; Pavlos G. Lagoudakis; Martin D. B. Charlton
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Paper Abstract

LED surface structuring has been widely used to increase light extraction[1]. Due to the high refractive index of the thick GaN epitaxy layers, most emitted light becomes trapped and reabsorbed by the epitaxial layers. While random structuring can effectively scatter trapped light out of the LED, it gives little control over the resulting beam-shapef[2]. Photonic crystals however provide a means to simultaneously improve light extraction efficiency and control beam directionality. Furthermore, P-side up LEDs normally utilize a transparent top contact layer in order to allow top light emission whilst maintaining good electrical properties. In this paper we investigate a novel photonic crystal LED configuration with a nontransparent metal top contact layer, and cylindrical holes etched through the top contact layer and deep into the underlying epitaxy. In this novel configuration light emission is only possible from the etched holes giving rise to extreme beam steering effects. We utilize broadband spectroscopic reflectometry to experimentally investigate beam shape and optical properties from fabricated devices. We observe a range of achievable beam patterns with extreme deviations from the normal Lambertian. We investigate the effect of square and triangular photonic crystal lattices on beam directionality.

Paper Details

Date Published: 25 February 2020
PDF: 8 pages
Proc. SPIE 11302, Light-Emitting Devices, Materials, and Applications XXIV, 113021P (25 February 2020); doi: 10.1117/12.2543124
Show Author Affiliations
Thomas M. Mercier, Univ. of Southampton (United Kingdom)
Chirenjeevi Krishnan, Univ. of Southampton (United Kingdom)
Peter J. Shaw, Univ. of Southampton (United Kingdom)
Pavlos G. Lagoudakis, Univ. of Southampton (United Kingdom)
Martin D. B. Charlton, Univ. of Southampton (United Kingdom)

Published in SPIE Proceedings Vol. 11302:
Light-Emitting Devices, Materials, and Applications XXIV
Jong Kyu Kim; Michael R. Krames; Martin Strassburg, Editor(s)

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