Electrical Properties of Thin-Film Semiconductors

The theory of the electrical properties of metal films as given by Fuchs and Sondheimer is extended to nondegenerate semiconductors with ellipsoidal energy surfaces. A change of variables reduces the problem to a simpler one with spherical energy surfaces but with electric and magnetic fields which are tilted with respect to the film. This is solved to first order in the applied fields. The effective mobility and Hall coefficient vary with film thickness much as for a metal but show an anisotropy with film orientation, even for cubic crystals. Anisotropy is observed for both diffuse and specular surface scattering and for surface channels as well as films, and it provides a means of measuring the effective mass ratio of the carriers.