Tight-binding calculation of spin splittings in semiconductor superlattices

Abstract

The spin splitting near the Γ point of the lowest ${\mathrm{\Gamma }}_1$-like conduction band of GaAs/AlAs superlattices with different growth orientations was calculated using the empirical tight-binding method. These microscopic calculations confirm the existence of a linear k term in the splitting arising from the confinement of the wave function in the GaAs wells. The tight-binding results are reproduced well by macroscopic k⋅p calculations for superlattices with large periods. The deviations found for small periods are attributed to the inadequacy of the effective-mass approximation used in the k⋅p calculations and to band mixing due to the superlattice periodicity.