  We examine the effects of interface roughness and/or planar impurity doping
in a superlattice, in the frame of a weak disorder description. We find that
these two types of disorder are equivalent, and that they can be viewed as
effective "bulk" disorder, with anisotropic diffusion coefficients. Our results
offer quantitative insight to transport properties of multilayers and devices,
which contain inadvertently structural disorder at the interfaces.
