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 + H2 ambient. The influence of H2 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 H2 flow ratio. The resistivity significantly decreases with increasing the H2 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 H2 addition. We suggest that there exist a large number of acceptors in the films, the introduced H2 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.