Correlation between luminescence properties of AlxGa1-xAs/GaAs single quantum wells and barrier composition fluctuation

The luminescence mechanism at low temperatures in AlxGa1-xAs/GaAs single quantum wells grown by molecular-beam epitaxy with different aluminum concentrations in the barrier has been studied in detail using the photoluminescence spectroscopy (PL) as function of temperature (8 K <= T <= 90 K) combined with the excitation intensity. The asymmetry presented by the PL spectra at the low-energy side, the blueshift behavior of the PL peak energy, and the PL line broadening with increasing temperature are explained through the exciton localization in confinement potential fluctuations. The exciton localization effects on the PL spectra are progressively reinforced with the increase of the Al concentration in the barrier constituent material. The PL peak energy dependence on temperature has been fitted through the expression proposed by Passler [Phys. Status Solidi B 200, 155 (1997)] adapted to systems with potential fluctuations, by subtracting the term sigma(2)(E)/k(B)T, where sigma(E) is the standard deviation of the potential fluctuations. It was verified that sigma(E) increases systematically with the Al concentration in the barrier, according to the AlGaAs alloy compositional disorder theory. (c) 2007 American Institute of Physics.