Magneto-optical properties of GaAsSb/GaAs quantum wells

We have measured the diamagnetic shift of a heavy-hole exciton in a single 60 Angstrom wide GaAs0.7Sb0.3/GaAs quantum well as a function of magnetic field up to 32 T at 1.3 K using photoluminescence spectroscopy. The sample was grown on (001)-oriented GaAs substrate using solid-source molecular beam epitaxy. We have calculated the variation of the diamagnetic shift as a function of magnetic field using a variational approach and a free exciton model. We assumed a weak type-I conduction-band lineup in our calculations. We found that the values thus obtained are more than twice as large as the observed values. A similar calculation assuming a complete localization of the heavy hole leads to the values of the diamagnetic shift which agree very well with the experimental data. Our study suggests that the excitons are strongly localized in GaAs0.7Sb0.3/GaAs quantum well structures at low temperatures, and that this heterostructure has a weak type-I conduction-band lineup. (C) 2003 American Institute of Physics.