Induced absorption spectroscopic determination of exciton binding energies in type-II GaAs/AlAs superlattices

The binding energies of magnetoexcitons in a range of GaAs/AlAs type-II superlattices have been measured directly for the first time, using a novel induced far-infrared absorption technique. Zero-field binding energies in the range 13.2--17.4 meV are found, and these are in excellent agreement with recently published variational calculations. Good fits to the experimental data in the range B=0--8 T are obtained with a modified quasi-two-dimensional magnetoexciton theory, allowing exciton dimensionality parameters to be determined.