Electronic Properties of Vapor-Grown Heteroepitaxial ZnO Film on Sapphire

Abstract

Hall coefficient and resistivity measurements have been made on single-crystal ZnO films prepared by chemical vapor deposition on sapphire substrates from 4.2 K to 300 K. Successive reduction of the film thickness from the surface and the rear (interface to substrate) revealed that there are two regions–a bulk region and an interfacial region adjacent to the substrate. At the interfacial region, the carrier density is assumed to be very high and impurity-band conduction takes place. The dependence of the mean resistivity and the mean carrier density on the film thickness and temperature are described well by the two-layer and two-band model.