Stretched exponential profiles of photoluminescence decays related to localized states in InGaAsN/GaAs single-quantum wells

We have investigated photoluminescence (PL) dynamics related to localized states in InxGa1-xAs1-yNy/GaAs single-quantum wells (SQWs) with the constant In content of x = 0.32 and various N contents of y = 0, 0.004, and 0.008. In order to determine the intrinsic band-edge energy, we used photoreflectance (PR) spectroscopy that is sensitive to the optical transitions at critical points. From systematic measurements of the PL and PR spectra, it is demonstrated that the slight incorporation of nitrogen considerably disorders the band-edge states of the InGaAsN SQWs, resulting from formation of localized states, so-called band-tail states. We find that the PL-decay profile related to the localized states generally exhibits a stretched exponential behavior peculiar to a disordered system at low temperatures, which means that randomness of alloy potential fluctuations including nitrogen dominates the PL dynamics. (c) 2006 Elsevier B.V. All rights reserved.