Photoluminescence and photoreflectance study of InGaAs/AlAsSb quantum wells grown by molecular-beam epitaxy

We report here on a photoluminescence (PL) and photoreflectance (PR) study in which we examined InGaAs/AlAsSb multiple quantum wells (MQWs) with both arsenic- and antimony-terminated interfaces that were grown by molecular-beam epitaxy. The PL spectra of the As-terminated MQWs are dominated by near-band-edge PL peaks over the temperature range between 8 and 300 K. The PL line shape and the temperature evolution of their PL peak energy show clear evidence of a feature that is characteristic of a band-tail localized exciton emission below 40 K. Conversely, the PL spectra of the Sb-terminated MQWs show broad spectra and also show excitation power dependence. Both samples show clear features that are characteristic of QW-related interband transitions in the PR spectra. The observed QW transition energies correspond well with the calculated interband transition energies. The temperature evolutions of the PR peak energies for both samples correspond well with the temperature dependence of the InGaAs bandgap. Although the PL peak energies correspond well with the PR peak energies at high temperature, Stokes shifts of 20 to 30 meV were observed at lower temperature, indicating strong localization of excitons due to potential fluctuations. The broad PL peak and the low activation energy that we observed for the PL integrated intensity quenching process suggest that enhanced incorporation of nonradiative centers at the InGaAs/AlAsSb interfaces was induced by the Sb interface termination. (C) 2004 American Institute of Physics.