Electronic transport in a superlattice with average periodic order

We introduce a model to describe scattering from disordered metallic interfacial regions in layered structures, or superlattices. This model is also applicable to interface roughness or boundary scattering in single junctions. It consists of an array of slabs of scattering centers embedded in a host metal. The slabs have thickness t and are separated by a distance d. Each simulates an interfacial region in which the physical arrangement of scattering centers is disordered with positional correlations within a slab being represented by a structure factor S, but atomic positions being uncorrelated between slabs. For a description of the structure factor of a slab with assumed quenched disorder, the pair correlation function for homogeneous liquids is used as an input after extension both to finite geometry and into regions of high density typical of solids. The Boltzmann equation, with the anisotropic structural information incorporated in the collision term, is solved by a variational principle, and yields the in-plane and out-of-plane resistivity and thermopower components as functions of d, t, and the density of scattering centers in a slab. The results show that it is possible to characterize the microscopic structural features of the interfacial region in terms of the transport properties of the system.