HOLE STATES IN GAAS/ALAS HETEROSTRUCTURES AND THE LIMITATIONS OF THE LUTTINGER MODEL

We present microscopic results for hole scattering at a [001] GaAs-AlAs single interface, with k(parallel-to) = 0, which show strong bulk light hole - heavy hole mixing. The hole scattering process is found to be due to the differences in the cell periodic wavefunctions of the materials of the interface, invalidating the fundamental assumption of the effective mass theory of hole states in heterostructures. We show that the mixing of light- and heavy-hole states is much larger than that obtained from a phenomenological model based on the Luttinger Hamiltonian. The time reversal symmetry aspects of bulk Bloch spinor states, in the presence of the spin-orbit interaction, are found to play an important role in determining the magnitude of the scattering amplitudes of the various bulk states. In the light of these calculations, we question the validity of the effective mass theory/Luttinger Hamiltonian approach, usually employed to describe heterostructure hole states.