Influence of H2 introduction on properties in Al-doped ZnO thin films prepared by RF magnetron sputtering at room temperature

Al-doped ZnO (AZO) thin films were prepared by RF magnetron sputtering on quartz substrates at room temperature in different Ar + H-2 ambient. The influence of H-2 flow ratio on the structure and optoelectronic properties in AZO films was investigated. The prepared films are hexagonal wurtzite structure with c-axis preferred orientation, and the intensity of (002) peak decreases with the increase of H-2 flow ratio. The resistivity significantly decreases with increasing the H-2 flow ratio to 1.0 % by almost four orders of magnitude. X-Ray photoelectron spectroscopy and X-ray diffraction measurements exhibit that the effectiveness of Al doping in the substitutional positions is not influenced by H-2 addition. We suggest that there exist a large number of acceptors in the films, the introduced H-2 will passivate the acceptors, which raises both carrier concentration and Hall mobility. The increase of carrier concentration consequently induces the blue shift of optical absorption edge according to the Burstein-Moss effect.