Charge transfer magnetoexcitons in magnetoabsorption spectra of asymmetric type-II double quantum wells

Charge-transfer excitons are studied by magneto-optical spectroscopy on (Ga,In)As/GaAs/Ga(As,Sb) asymmetric type-II double quantum well heterostructures grown by metal-organic vapor phase epitaxy. Several charge-transfer magnetoexciton resonances are clearly resolved in the optical absorption spectra. The dependence of the energies and the oscillator strengths of the exciton ground state and excited exciton states on the magnetic field are studied. For small magnetic fields, a diagmagnetic shift proportional to ${B}^{2}$ dominates, which for larger magnetic fields continuously changes into a linear dependence due to Landau quantization. The measured spectral shifts and the increase in oscillator strengths with magnetic field are in very good agreement with microscopic theoretical simulations. Our results thus demonstrate that magnetoexcitons exist in type II quantum well structures, where the electrons and holes are spatially separated and localized in different quantum wells, and we analyze their properties and tunability over a broad range of field strength. Thereby, we provide a detailed analysis of the properties of magnetoexcitons in type-II quantum well structures, where the electrons and holes are spatially separated and localized in different quantum wells, and demonstrate their tunability over a broad range of field strengths.