Berlin 2008 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 45: GaN devices

HL 45.8: Talk

Thursday, February 28, 2008, 11:15–11:30, EW 202

Effect of the barrier composition on the efficiency and emission spectra of GaN-based near ultraviolet light emitting diodes — •T. Kolbe¹, A. Knauer², V. Küller², S. Einfeldt², J. R. van Look¹, P. Vogt¹, M. Weyers², and M. Kneissl^1,2 — ¹TU Berlin, Institute of Solid State Physics, Hardenbergstr. 36, 10623 Berlin, Germany — ²Ferdinand-Braun-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin, Germany

Light Emitting Diodes (LEDs) based on III-nitride semiconductors have attracted great interest in recent years. Carrier confinement, piezoelectric fields and a low external quantum efficencies are particularly problematic for ultraviolet LEDs.
Here we present continuous wave and pulsed electroluminescense measurements of GaN-based multi quantum well LEDs with different barrier compositions. These devices were grown by metalorganic vapour phase epitaxy on (0001) sapphire substrates. The emission wavelength is approximately 375nm for an active region comprised of In_0.03Ga_0.97N quantum wells (QWs) and surrounded by GaN, Al_0.16Ga_0.84N or In_xAl_0.16GaN barrier layers. We found that the blue-shift of the emission wavelength related to the piezoelectric field in the QWs and the resulting quantum confined Stark effect (QCSE) clearly depends on the barrier composition and is zero for samples with lattice matched In_0.04Al_0.16Ga_0.80N barrier. An InAlGaN barrier with 3.3% indium resulted in a 50-fold increase of output power compared to LEDs with GaN barriers.