Energy levels of Wannier excitons in a quantum-well structure consisting of a single slab of GaAs sandwiched between two semi-infinite layers of Gal "Al"As are calculated with the use of a variational approach. Owing to lowering of symmetry along the axis of growth of this quantum-well structure and the presence of energy-band discontinuities at the interfaces, the degeneracy of the valence band of GaAs is removed, leading to two exciton systems, namely, the heavy-hole exciton and the light-hole exciton. The values of the binding energies of the ground state and of a few lowlying excited states of these two exciton systems are calculated as a function of the size of the GaAs quantum well for several values of the heights of the potential barriers and their behavior is discussed. The results thus obtained are also compared with the available experimental data. The reliability of the various approximations made in this calculation is discussed.

In this work we present the calculation of the excitonic transition energies in ZnO/MgZnO quantum well heterostructures, accounting for the effects of the exciton–phonon interaction. The results of our calculations clearly show that the description of the electron–hole interaction by means of the static screened Coulomb potential and the use of the polaron masses for the electron and the hole leads to a poor agreement with available experimental data. On the other hand, including the exciton–phonon interaction in the calculation of the exciton binding energies, leads to the values of the excitonic transitions which agree very well with the recently published experimental data. A critical discussion of the choice of the physical parameters used in ZnO is also presented, which leads us to suggest a value for the heavy-hole band mass of 0.78m0 and a conduction-valence band ratio in the range 60/40–70/30.

We present a calculation of the variation of the binding energy of a heavy-hole exciton in a highly ionic quantum well structure, as a function of well width using a variational approach. We include the effects of exciton-phonon interaction and of mismatches between the particle masses and the dielectric constants of the well and barrier layers. The effect of exciton-phonon interaction is described in terms of an effective potential between the electron and the hole, derived by Pollmann and Büttner ͓J. Pollmann and H. Büttner, Phys. Rev. B 16, 4480 ͑1977͔͒ using an exciton-bulk optical-phonon Hamiltonian. We find that the values of the exciton binding energies we calculate agree very well with those obtained using a more rigorous but a complicated approach due to Zheng and Matsuura ͓R. Zheng and M. Matsuura, Phys. Rev. B 58, 10 769 ͑1998͔͒ in which they consider an exciton interacting with the confined-longitudinal optical phonons, interface phonons, and half-space phonons. Our method has the advantage of being considerably simpler, more efficient to use and is much easier to generalize to include the effects of external perturbations such as electric and magnetic fields. We compare the results of our calculations with the available experimental data in a few ionic quantum well structures and find a very good agreement. We show that for an appropriate understanding of the experimental data in ionic quantum well structures one must properly account for the exciton-phonon interaction.

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