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13 February 2007 Measurement of the internal quantum efficiency of InGaN quantum wells
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The internal quantum efficiency as a function of the internal electric field was studied in InGaN/GaN based quantumwell heterostructures. Most striking, we find the IQE to be independent of the electron hole overlap for a standard green-emitting single quantum-well LED structure. In standard c-plane grown InGaN quantum wells, internal piezo-fields are responsible for a reduced overlap of electron and hole wavefunction. Minimization of these fields, for example by growth on non-polar m- and a-planes, is generally considered a key to improve the performance of nitride-based light emitting devices. In our experiment, we manipulate the overlap by applying different bias voltages to the standard c-plane grown sample, thus superimposing a voltage induced band-bending to the internal fields. In contrast to the IQE measurement, the dependence of carrier lifetime and wavelength shift on bias voltage could be explained solely by the internal piezo-fields according to the quantum confined Stark effect. Measurements were performed using temperature and bias dependent resonant photoluminescence, measuring luminescence and photocurrent simultaneously. Furthermore, the doping profile in the immediate vicinity of the QWs was found to be a key parameter that strongly influences the IQE measurement. A doping induced intrinsic hole reservoir inside the QWs is suggested to enhance the radiative exciton recombination rate and thus to improve saturation of photoluminescence efficiency.
© (2007) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
A. Laubsch, M. Sabathil, G. Bruederl, J. Wagner, M. Strassburg, E. Baur, H. Braun, U. T. Schwarz, A. Lell, S. Lutgen, N. Linder, R. Oberschmid, and B. Hahn "Measurement of the internal quantum efficiency of InGaN quantum wells", Proc. SPIE 6486, Light-Emitting Diodes: Research, Manufacturing, and Applications XI, 64860J (13 February 2007);

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