EXCITON-STATES IN TYPE-I AND TYPE-II GAAS GA1-XALXAS SUPERLATTICES

We develop an expression for the exciton envelope function in a superlattice in terms of localized exciton Wannier functions. Through an expansion of the Wannier functions in the basis of two-well exciton states, we present the exciton minibands in the type-I GaAs/Ga0.7Al0.3As superlattice and the confinement-induced type-II GaAs/AlAs superlattice. We also calculate the absorption coefficient for the type-I system. We find that our binding energies are in good agreement with experimental results down to layer thicknesses of 30 AI. © 1990 The American Physical Society.