Effects of Cu–Zn phases on electronic properties in ZnO:Cu films

Theory predicts Cu‐doped ZnO (ZnO:Cu) has p ‐conductivity; however, this has only been demonstrated in a small number of experimental and mechanistic studies. In this paper, ZnO:Cu films were grown in situ with varying Cu content, prepared using radiofrequency atomic source–assisted molecular‐beam vapor deposition. The results indicate that ZnO:Cu films with dopant of Cu 2+ only had n ‐type behavior. As the Cu content increased, Cu + was the major dopant and the ZnO:Cu films had p ‐type behavior. However, excess Cu dopant resulted in the formation of second phases of Cu 2 O and Cu–Zn. The formation of a Cu–Zn phase increased the content of Zn vacancy, thus increasing hole concentration. Stronger alloy scattering decreased carrier mobility. Therefore, Cu + dopant and Zn vacancy give ZnO:Cu films p ‐conductivity properties.