Influence of the barrier composition on the light output of InGaN multiple-quantum-well ultraviolet light emitting diode
A. Knauera, V. Kuellera, S. Einfeldta, T. Kolbeb, J.-R. van Lookb, V. Hoffmanna, J. Piprekc, M. Weyersa and M. Kneissla,b
Published in:
Proc. SPIE, vol. 6797, no. 67970X-1 (2007).
Abstract:
MOVPE grown InGaN multiple-quantum-well (MQW) light emitting diodes (LEDs) on c-plane (0001) sapphire emitting at 375 nm with GaN, Al0.16Ga0.84N and InxAl0.16GaN-barrier layers were investigated in order to study the influence of the barrier composition on the light output characteristics of near UV devices. By substituting the GaN barrier layers with Al0.16Ga0.84N the output power increased 30-fold due to the increased band-offset between the In0.03Ga0.97N QWs and the barriers. The addition of 3.3% indium to the AlGaN barriers resulted in a reduction of the FWHM, and a 50-fold increase in light output power compared to LEDs with GaN barriers. Even though the band-offset and hence the carrier confinement for the InAlGaN barriers is smaller than in the case of AlGaN barriers, strain compensated In0.03Al0.16Ga0.79N barrier layers seem to be greatly beneficial for the external quantum efficiency of the near UV LEDs. The effect of an n-type Al0.23Ga0.77N hole-blocking-layer, which was inserted below the MQW stack to prevent hole carrier leakage from UV LED active region, on the light output was also investigated. By incorporating strain compensated In0.03Al0.16Ga0.79N barriers and an Al0.23Ga0.77N hole blocking layer we were able to realize 375 nm LEDs with an output of 1 mW (measured on-wafer) at 100 mA. Finally, the wavelength dependence of the light output from UV LEDs with InGaN MQWs emitting between 375 nm and 381 nm with peak output power of 4 mW at 200 mA for the longer wavelength devices is shown.
a Ferdinand-Braun-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin, Germany
b Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstr. 36, 10623 Berlin, Germany
c NUSOD Institute, PO Box 7204, Newark, Delaware 19714, United States
Keywords:
UV LED, InGaN-MQW, InAlGaN, MOVPE, strain compensation, light output
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