WANNIER EXCITONS IN ASYMMETRICAL QUANTUM-WELL STRUCTURES

Binding energies of excitons in asymmetrical quantum well systems are calculated by a perturbative approach based on the effective-mass appr oximation in the envelope function scheme. We studied the effects of a composition, a longitudinal uniform electric field and geometrical pa rameters of AlxGa1-xAs/GaAs quantum well structures on the exciton bin ding energies. It is shown that, in specially selected structures, cer tain excitons may be absent inside rather wide domains of a compositio n or an electric field.