VALLEY MIXING IN SHORT-PERIOD SUPERLATTICES AND THE INTERFACE MATRIX

Energy levels of short-period GaAs/AlAs superlattices are calculated both in an sps * tight-binding model and in an effective-mass approximation. Mixing between GAMMA and X conduction-band valleys is shown to be successfully described by a current-conserving interface matrix giving boundary conditions among envelope functions and their derivatives at a heterointerface. Two parameters characterizing the mixing are determined.