Excitons in type-II quantum-well systems: Binding of the spatially separated electron and hole

Excitons in type-II quantum-well systems, i.e., in the configuration of the spatially separated electron and hole, are studied by the variational calculation of binding energies and spatial extensions with the use of the infinite-potential-barrier model. It is shown that (i) excitonic properties depend very much on the electron-hole mass ratio and the well widths and that (ii) the dimensional character of an exciton (such as two-dimensional 1s and the three-dimensional 2$p_z$ character) appears in some limits of these physical parameters of the system.