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Efficient 350 nm LEDs on low edge threading dislocation density AlGaN buffer layers

: Gutt, R.; Passow, T.; Pletschen, W.; Kunzer, M.; Kirste, L.; Forghani, K.; Scholz, F.; Klein, O.; Kaiser, U.; Köhler, K.; Wagner, J.

Fulltext urn:nbn:de:0011-n-1581864 (2.0 MByte PDF)
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Copyright 2011 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.
Created on: 15.8.2013

Streubel, K.P. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Light-emitting diodes: Materials, devices, and applications for solid state lighting XV : 25-27 January 2011, San Francisco, California, United States
Bellingham, WA: SPIE, 2011 (Proceedings of SPIE 7954)
ISBN: 978-0-8194-8491-8
ISBN: 0-8194-8491-1
Paper 79540Q
Conference "Light-Emitting Diodes - Materials, Devices, and Applications for Solid State Lighting" <15, 2011, San Francisco/Calif.>
Conference Paper, Electronic Publication
Fraunhofer IAF ()
LED; ultraviolet; AlGaN; MOVPE; dislocation

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 w-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.