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

A magneto-optical study of the energy and spin structure of charged excitons in a 20-nm-thick CdTe/Cd0.65Mg0.35Te 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-) 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 T+ and increases for T- with B. The triplet state of T+ is identified in strong fields with a binding energy smaller than that of the T- triplet state.