VALLEY MIXING IN GAAS ALAS MULTILAYER STRUCTURES IN THE EFFECTIVE-MASS METHOD/

We introduce a set of boundary conditions for electron envelope functi ons at GaAs/AlAs heterointerfaces so as to take into account GAMMA-X(z ) and X(x)-X(y) valley mixings in the effective-mass method. The propo sed conditions enable one to obtain the dependence of the mixing effec t upon the parity of monolayer numbers in AlAs and GaAs layers, in agr eement with the empirical model calculations. The tunneling probabilit y across a two-interfarce structure GaAs(AlAs)MGaAs(001) is calculated as a function of the GAMMA-electron energy. The electron transfer is shown to depend essentially on the parity of M. An analytical solution is obtained for the dispersion of mixed X(xy) minibands. Direct optic al transitions are allowed between these minibands in the in-plane lig ht polarization. The corresponding far-infrared absorption coefficient is calculated and estimated.