Positively versus negatively charged excitons: A high magnetic field study of CdTe/Cd1−xMgxTe quantum wells

Abstract

A magneto-optical study of the energy and spin structure of charged excitons in a 20-nm-thick CdTe/Cd${}_{0.65}$Mg${}_{0.35}$Te quantum well is performed in strong magnetic fields up to 51 T. The type of resident carriers (holes or electrons) in the quantum well is controlled optically by above-barrier illumination, permitting a direct comparison of positively (T${}^{+}$) versus negatively (T${}^{\ensuremath{-}}$) charged excitons. The binding energies of the singlet states of these complexes behave qualitatively differently with increasing magnetic field $B$; namely, the binding energy decreases for ${\mathrm{T}}^{+}$ and increases for ${\mathrm{T}}^{\ensuremath{-}}$ with $B$. The triplet state of ${\mathrm{T}}^{+}$ is identified in strong fields with a binding energy smaller than that of the ${\mathrm{T}}^{\ensuremath{-}}$ triplet state.