Dependence of material properties of radio-frequency magnetron-sputtered, Cu-doped, ZnTe thin films on deposition conditions

Abstract

Because of its ability to be doped highly p type, and because its valence-band discontinuity with CdTe is small, ZnTe is believed to have an important use as an interface layer for electrical contacts to crystalline and thin-film CdTe devices. Although this and other potential uses have been identified, relatively little is known about the fundamental properties of ZnTe in its thin-film form, and even less is known about possible effects specific to sputter deposition. In this study, we investigate the effects of deposition conditions on the compositional, electrical, optical, and structural properties of thin-film ZnTe produced by rf-magnetron sputtering. Results indicate that, as is often observed when sputtering high-vapor-pressure compounds, rf-sputtered ZnTe films are slightly Zn deficient. Although this may be undesirable when producing high-resistivity undoped films, it may be advantageous when producing low-resistivity p-type films because it may encourage incorporation of substitutional Group I dopants, such as Cu. We have determined that the choice of deposition parameters can indeed affect the stoichiometry of the sputtered ZnTe film, and that Cu can be used effectively as a p-type dopant. Additionally, we have been able to produce Cu-doped ZnTe with carrier concentrations in excess of 1020 cm−3.