Growth of high-quality Ga–F codoped ZnO thin films by mid-frequency sputtering

Ga and F codoping was applied by mid-frequency magnetron sputtering on glass substrates at room temperature to prepare ZnO-based thin films with excellent opto-electrical properties. The effects of deposition parameters including sputtering power and pressure were investigated by varying them from 200 W to 2300 W and from 0.1 Pa to 1.0 Pa, respectively. The as-deposited films had a polycrystalline structure and a strong preferred c-axis orientation. The strain state of the films was also determined by XRD analysis, and a residual stress of −1.08 GPa was obtained at 1300 W. A resistivity of as low as 6.4×10−4 Ω cm was achieved for the film deposited at 1300 W and 0.1 Pa. The optical performance of Ga–F-codoped ZnO films significantly improved compared with Al-doped ZnO films, exhibiting a high transmittance of >90%. Hall effect measurements showed that Ga and F addition led to increased carrier concentration for ZnO-based thin films.