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Proceedings Paper

Nonresonant-cavity light-emitting diodes
Author(s): Reiner Windisch; Maarten Kuijk; Barundeb Dutta; Alexander Knobloch; Peter Kiesel; Gottfried H. Doehler; Gustaaf Borghs; Paul L. Heremans
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Paper Abstract

The external efficiency of conventional light-emitting diodes (LED's) is limited by total internal reflection at the semiconductor-air interface. For conventional GaAs-based LED's, this results in an extraction efficiency of 2%. In non- resonant cavity (NRC) LED's, this problem is overcome by a combination of internal scattering at a textured top surface and reflection on a back mirror, which increases the probability of escape. Using this approach, we demonstrate external quantum efficiencies of up to 40% without encapsulation of the LED. To gain a more detailed understanding of the out-coupling mechanisms in NRC-LED's, the scattering properties of the textured surface are investigated experimentally. The optimum surface texture is found to randomize the direction of the internally reflected light almost perfectly. In addition, NRC-LED's also enables the enhancement of the external quantum efficiency for small and fast LED's. With efficiencies of about 15%, we demonstrate bitrates of more than 1.3 GBit/s. In order to modify the lambertian output characteristics, we have successfully applied microlenses, allowing 50% coupling efficiency into optical fibers with NA equals 0.5.

Paper Details

Date Published: 17 April 2000
PDF: 7 pages
Proc. SPIE 3938, Light-Emitting Diodes: Research, Manufacturing, and Applications IV, (17 April 2000); doi: 10.1117/12.382829
Show Author Affiliations
Reiner Windisch, IMEC (Germany)
Maarten Kuijk, Vrije Univ. Brussels (Belgium)
Barundeb Dutta, IMEC (Belgium)
Alexander Knobloch, Friedrich-Alexander Univ. Erlangen-Nuernberg (Germany)
Peter Kiesel, Friedrich-Alexander Univ. Erlangen-Nuernberg (Germany)
Gottfried H. Doehler, Friedrich-Alexander Univ. Erlangen-Nuernberg (Germany)
Gustaaf Borghs, IMEC (Belgium)
Paul L. Heremans, IMEC (Belgium)

Published in SPIE Proceedings Vol. 3938:
Light-Emitting Diodes: Research, Manufacturing, and Applications IV
H. Walter Yao; Ian T. Ferguson; E. Fred Schubert, Editor(s)

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