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Proceedings Paper

Optimization of semipolar GaInN/GaN blue/green light emitting diode structures on {1-101} GaN side facets
Author(s): T. Wunderer; J. Hertkorn; F. Lipski; P. Brückner; M. Feneberg; M. Schirra; K. Thonke; I. Knoke; E. Meissner; A. Chuvilin; U. Kaiser; F. Scholz
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Paper Abstract

Bluish-green semipolar GaInN/GaN light emitting diodes (LEDs) were investigated as possible candidates for high-brightness devices even in the long wavelength visible regime. To combine the high material quality known from c-GaN and the advantages of a reduced piezoelectric field, the LED structures were realized on the {1¯101} side facets of selectively grown GaN stripes with triangular cross section. Structural investigations using transmission electron microscopy, scanning electron microscopy, high resolution x-ray diffraction, and atomic force microscopy have been performed and could be related to the luminescence properties in photoluminescence and cathodoluminescence. The defect-related luminescence peaks at 3.3 eV and 3.42 eV typically observed in planar non- and semipolar GaN structures as fingerprints of prismatic and basal plane stacking faults, respectively, could be eliminated in our facet LED structures by optimized growth conditions. Furthermore, an indium incorporation efficiency for these {1¯101} facets is found to be about 50% higher as compared to c-plane growth, what helps significantly to achieve longer wavelength emission in spite of the reduced quantum confined Stark effect in such non- and semipolar materials. Combining these findings, we could realize a bluish-green semipolar light emitting diode on the side facets of our GaN stripes. Continuous wave on-wafer optical output powers as high as 240 µW@20mA could be achieved for about 500nm emission wavelength in electroluminescence measurements. The external efficiency was nearly constant for the investigated current range. Furthermore, the relatively small wavelength shift of about 3 nm for currents between 10mA and 100mA confirmed the reduced piezoelectric field in our LED structures.

Paper Details

Date Published: 28 February 2008
PDF: 9 pages
Proc. SPIE 6894, Gallium Nitride Materials and Devices III, 68940V (28 February 2008); doi: 10.1117/12.763400
Show Author Affiliations
T. Wunderer, Ulm Univ. (Germany)
J. Hertkorn, Ulm Univ. (Germany)
F. Lipski, Ulm Univ. (Germany)
P. Brückner, Ulm Univ. (Germany)
M. Feneberg, Ulm Univ. (Germany)
M. Schirra, Ulm Univ. (Germany)
K. Thonke, Ulm Univ. (Germany)
I. Knoke, Fraunhofer IISB (Germany)
E. Meissner, Fraunhofer IISB (Germany)
A. Chuvilin, Ulm Univ. (Germany)
U. Kaiser, Ulm Univ. (Germany)
F. Scholz, Ulm Univ. (Germany)

Published in SPIE Proceedings Vol. 6894:
Gallium Nitride Materials and Devices III
Hadis Morkoç; Cole W. Litton; Jen-Inn Chyi; Yasushi Nanishi; Euijoon Yoon, Editor(s)

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