We report the first full-scale calculation of the subband structure along the cubic axes of GaAs-AlAs superlattices with microscopically imperfect interfaces. We show that the valley-mixing effects can be used as a sensitive probe of the interface disorder whose characteristic dimension is of order of the bulk lattice constant. It would appear that our predictions concerning the effect of disorder on the optical spectra of small-period structures are in close agreement with recent experimental data.

• Received 6 August 1990

DOI:https://doi.org/10.1103/PhysRevB.42.11818