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Emission characteristics of InGaN multi quantum well light emitting diodes with differently strained InAlGaN barriers
T. Kolbe1, A. Knauer2, H. Wenzel2, S. Einfeldt2, V. Kueller2, P. Vogt1, M. Weyers2, and M. Kneissl1,2
1 Institute of Solid State Physics, Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin, Germany
2 Ferdinand-Braun-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Straße 4, 12489 Berlin, Germany
Published in:
phys. stat. sol. (c), vol. 6, no. S2, pp. S889-S892 (2009).
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Abstract:
In this paper we report on the emission characteristics of In-
GaN multi quantum well light emitting diodes (LEDs) in the
near ultra-violet (UV) spectral range. GaN, AlGaN and InAl-
GaN with various indium contents were compared as barrier
material in the InGaN quantum well active region of the device
heterostructure. It was found that the emission wavelength
decreases with increasing drive current. This blue shift
with an increasing indium content in the quaternary barriers
can be attributed to the screening of the polarization fields
and band gap renormalization. Light emitting diodes with a
constant emission wavelength over a wide current range were
realized by using nearly lattice matched InAlGaN barriers.
These devices also showed the highest light output power
even though the band offset between the quantum wells and
the barriers is smaller in comparison to the LEDs with the
AlGaN barriers. These effects can be explained by the interplay
of a reduction defect density at the quantum well/barrier
interface and a improved overlap of the electron and hole
wave functions due to the reduction of quantum confined
Stark effect.
PACS:
77.65.Ly, 78.60.Fi, 78.67.De, 81.07.St, 85.35.Be, 85.60.Jb
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