Investigation on Na-N dual acceptors doped p-type ZnCdO thin films synthesized by RF magnetron sputtering

Sodium and nitrogen dual acceptors doped ZnCdO [ZCO:(Na, N)] have been prepared by radio frequency (RF) reactive magnetron sputtering followed by rapid annealing treatment, and the influence of the ratio of argon to nitrogen gas flow (Ar:N2) on the electrical, structure and optical properties of ZCO:(Na, N) films were investigated in detail. Hall-effect measurement results reveal that Na-N dual acceptors doping method is an effective path to realize the p-type conversion of ZnCdO (ZCO). When the Ar:N2 was set to 1:2 (S3), ZCO:(Na, N) film possesses the optimal p-type conduction properties with carrier concentration of 7.84 × 1018 cm−3 and the resistivity of 30.9 Ω cm. It is demonstrated that the presence of NaZn and No acceptors are answerable for the p-type behavior in ZCO:(Na, N) film by the analysis of X-ray photoelectron spectroscopy (XPS) results. All the ZCO:(Na, N) films are of hexagonal wurtzite crystal structure with highly (002) preferential orientation. As Ar:N2 increases from 1:4 (S1) to 2:1 (S5), the absorption edge gradually shifted to longer wavelength side. The observed p-type ZCO:(Na, N) films will open the door for practical applications in various optoelectronic devices.