Extra-low resistivity in N and H doped Cu2O thin films grown by room temperature RF sputtering

Abstract

Cuprous oxide (Cu₂O) is an intrinsic p-type semiconductor representing an interesting, potential hole transporting material in 3rd generation solar cells. However, its practical applications are significantly limited by its intrinsically high resistivity. In the present study, we show that polycrystalline Cu₂O thin films with an extra-low resistivity of 0.16 Ω cm can be grown by radio frequency (RF) sputtering by exploiting the effects of nitrogen and hydrogen doping. Significantly and differently from previous studies, the films are deposited at room temperature and the material doping is performed through the simultaneous introduction of both dopants in the Cu₂O films during the growth process. The effects of N and H dopants on the Cu₂O properties are investigated by performing resistivity, Hall effect, UPS, X-ray Diffraction and Raman measurements on a pristine Cu₂O film, on Cu₂O films doped with N and H individually, as well as on films containing both dopants. Such a systematic investigation of the doping effects permits to perform a comparative analysis of the achieved results and data from literature and to develop an exhaustive, interpretative framework that clarifies the role of native defects and N and H dopants in reducing the resistivity of Cu₂O.