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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