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A study was conducted on potential fluctuations using the photoluminescence (PL) technique with temperature and excitation intensity variations, in a sample containing InGaAs/InGaAlAs coupled double quantum wells, with spikes of InGaAlAs of different thicknesses, and a single quantum well as the control. With the inclusion of a spike at the center of the well, an increase in the magnitude of the potential fluctuation occurs, in relation to the control well, due to an increase in the contribution from both the interface roughness and the compositional disorders to the potential fluctuations. The enhancement of the effects of the potential fluctuations, such as the PL linewidth and the blueshift of the PL peak energy with the temperature, as the spike thickness increases, was attributed to the increase in the contribution from the alloy composition fluctuation to the potential fluctuation, caused by an increase in the interaction of the wave function with the central and lateral barriers. This study also discusses the strong influence of the excitation intensity on the variation of the emission energy with temperature. [ABSTRACT FROM AUTHOR]

AlGaAs structures with different aluminum concentration (x=0.0, 0.17, 0.30, and 0.40) were characterized by photoluminescence and photoreflectance techniques. The temperature dependence of optical transitions in the temperature ranging from 2 to 300 K were investigated. Y. P. Varshni [Physica (Utrecht) 34, 194 (1967)], L. Vin˜a et al. [Phys. Rev. B 30, 1979 (1984)], and R. Pa¨ssler [Phys. Status Solidi B 200, 155 (1997)] models were used to fit the experimental points. The Pa¨ssler model gave the best adjustment to the experimental points. The tree models showed that the empirical parameters obtained through the adjustment of the experimental data in the three different models are aluminum composition dependent in the ternary alloy. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

AlGaAsSb/AlAsSb Bragg mirrors lattice matched on InP with six pairs of layers were grown by molecular beam epitaxy. The effect of Te doping on the electrical and optical properties of the Bragg mirrors, and the presence of digital alloy gradient layers between the ternary and quaternary layers are analysed. The presence of digital alloy layers at the interfaces reduces the electrical resistance through the perpendicular direction of the Bragg mirror, without significantly affecting the reflectivity. [Copyright &y& Elsevier]