  A method is proposed to find the wave function of an electron moving
infinitely in the field of an arbitrary 1D layer structure with two different
homogeneous semi-infinite boundaries. It is shown that in general the problem
reduces to solution of a set of two linear difference equations. The proposed
approach is discussed on a base of two cases: a structure of periodically
placed identical rectangular potentials and a non-ordered structure with
certain distortion of periodicity and potential identity.
