Magnetoabsorption and spin polarization inversion in GaAs/AlGaAs quantum wells

The impact of the growth orientation on spin dynamics in GaAs/AlGaAs quantum wells (QWs) is explored through magnetophotoluminescence measurements. Samples grown on both (100) and (311)A GaAs surfaces exhibit intensity oscillations at high magnetic fields, characteristic of magnetoabsorption arising from interband transitions between Landau levels when excited near resonance. Notably, the (311)A surface reveals optical responses rarely observed on the conventional (100) surface, including an inversion in circular polarization degree influenced by both excitation power and temperature. To elucidate these findings, we develop an eight-level model encompassing electron and hole excited states. Our analysis demonstrates that thermalization is the primary and sufficient factor responsible for reproducing spin inversion with external parameters.