Transport Phenomena in Semiconducting Thin Films

Transport phenomena in thin semiconducting films are studied using the transport equation, the quantization of the transverse motion of the electrons being taken into account. A general formula relating the relaxation time for a thin film to that for the bulk semiconductor is obtained. The mobility is found to increase as the film thickness decreases. Hence the increase of the resistivity with decreasing film thickness does not in general indicate increasing imperfection density. It is found that the Hall constant is only weakly dependent on the film thickness. The transport effects in thin semiconducting films and in bulk semiconductors are compared for several scattering mechanisms.