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Proceedings Paper

Efficient 350 nm LEDs on low edge threading dislocation density AlGaN buffer layers
Author(s): Richard Gutt; Thorsten Passow; Wilfried Pletschen; Michael Kunzer; Lutz Kirste; Kamran Forghani; Ferdinand Scholz; Oliver Klein; Ute Kaiser; Klaus Köhler; Joachim Wagner
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Paper Abstract

Improving the crystal quality of AlGaN epitaxial layers is essential for the realization of efficient III-nitride-based light emitting diodes (LEDs) with emission wavelengths below 365 nm. Here, we report on two different approaches to improve the material quality of AlGaN buffer layers for such UV-LEDs, which are known to be effective for the MOVPE growth of GaN layers. Firstly, we grew AlGaN on thin GaN nucleation islands which exhibit a threedimensional facetted structure (3D GaN nucleation). Lateral overgrowth of these islands results in a lateral bending of dislocation lines at the growing facets. Secondly, in-situ deposited SiNx interlayers have been used as nano-masks reducing the dislocation density above the SiNx layers. Both approaches result in reduced asymmetric HRXRD ω-scan peak widths, indicating a reduced edge-type dislocation density. They can be applied to the growth of AlGaN layers with an Al concentration of at least 20%, thus suitable for LEDs emitting around 350 nm. On-wafer electroluminescence measurements at 20 mA show an increase in output power by a factor of 7 and 25 for LED structures grown on 3D GaN nucleation and SiNx interlayer, respectively, compared to structures grown on a purely 2D grown low Al-content AlGaN nucleation layer. Mesa-LEDs fabricated from the LED layer sequences grown on buffers with SiNx interlayer exhibit a low forward voltage of 3.8 V at 20 mA and a maximum continuous wave (cw) output power of 12.2 mW at 300 mA.

Paper Details

Date Published: 9 February 2011
PDF: 8 pages
Proc. SPIE 7954, Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XV, 79540Q (9 February 2011); doi: 10.1117/12.873531
Show Author Affiliations
Richard Gutt, Fraunhofer-Institut für Angewandte Festkörperphysik (Germany)
Thorsten Passow, Fraunhofer-Institut für Angewandte Festkörperphysik (Germany)
Wilfried Pletschen, Fraunhofer-Institut für Angewandte Festkörperphysik (Germany)
Michael Kunzer, Fraunhofer-Institut für Angewandte Festkörperphysik (Germany)
Lutz Kirste, Fraunhofer-Institut für Angewandte Festkörperphysik (Germany)
Kamran Forghani, Univ. Ulm (Germany)
Ferdinand Scholz, Univ. Ulm (Germany)
Oliver Klein, Univ. Ulm (Germany)
Ute Kaiser, Univ. Ulm (Germany)
Klaus Köhler, Fraunhofer-Institut für Angewandte Festkörperphysik (Germany)
Joachim Wagner, Fraunhofer-Institut für Angewandte Festkörperphysik (Germany)

Published in SPIE Proceedings Vol. 7954:
Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XV
Klaus P. Streubel; Heonsu Jeon; Li-Wei Tu; Norbert Linder, Editor(s)

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