Magneto-optical spectroscopy of positively charged excitons in GaAs quantum wells

We report observation of positively charged excitons (${\mathit{X}}^{+}$) in GaAs quantum wells remotely doped with acceptors. Upon reducing the excess hole density, by photoexciting carriers in the doped barrier layer, we observe the neutral excitonic transition strengthen relative to ${\mathit{X}}^{+}$. Further confirmation of the ${\mathit{X}}^{+}$ assignment is provided by its temperature and magnetic-field dependence. We observe both the antisymmetric (singlet) and symmetric (triplet) ${\mathit{X}}^{+}$ spin states.