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Enhancement of light extraction in ultraviolet light-emitting diodes using nanopixel contact design with Al reflector
N. Lobo1, H. Rodriguez2, A. Knauer2, M. Hoppe2, S. Einfeldt2, P. Vogt1, M. Weyers2, and M. Kneissl1,2
1 Institute of Solid State Physics, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany
2 Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Straße 4, 12489 Berlin, Germany
Published in:
Appl. Phys. Lett., vol. 96, no. 081109 (2010).
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Abstract:
We report on a nanopixel contact design for nitride-based ultraviolet light-emitting diodes to
enhance light extraction. The structure consists of arrays of Pd ohmic contact pixels and an
overlying Al reflector layer. Based on this design a twofold increase in the light output, compared
to large area Pd square contacts is demonstrated. Theoretical calculations and experiments reveal
that a nanopixel spacing of 1 µm or less is required to enable current overlap in the region between
the nanopixels due to current spreading in the p-GaN layer and to ensure current injection into the
entire active region. Light emitted in the region between the nanopixels will be reflected by the Al
layer enhancing the light output. The dependence of the light extraction on the nanopixel size and
spacing is investigated.
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