Origin of the green gap: Increasing nonradiative recombination in indium-rich GaInN/GaN quantum well structures

Using time-resolved photoluminescence spectroscopy on GaInN/GaN multiple quantum well structures, we analyze the radiative and nonradiative processes contributing to the green gap in GaN-based light emitting devices. We observe that it is only partly caused by a reduced oscillator strength due to the Quantum Confined Stark Effect (QCSE) which becomes stronger with increasing indium concentration and well width. As the dominant effect we observe a reduction of nonradiative lifetimes when the indium concentration is increased. For higher indium concentrations, we find an additional nonradiative recombination path that might be attributed to an increased generation of defects like misfit dislocations, nitrogen vacancies and/or indium clusters within the optically active region. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim