Study of H-related defects in Ga-doped ZnO thin films deposited by RF magnetron sputtering in Ar+H-2 ambient

摘要

H-related defects have been investigated in Ga-doped ZnO thin films deposited by RF magnetron sputtering at room temperature in Ar+H-2 ambient. When the flow ratio of H-2/(Ar+H-2) increases from 0 to 4%, the resistivity significantly decreases from 194 x 10(-2) to 569 x 10(-4) Omega cm. X-ray diffraction and X-ray photoelectron spectroscopy results show that it should not be ascribed to the films' crystalline quality, the chemical states and substitutional situation of Ga and Zn. It is suggested that there are a large number of acceptors in the films, the major role of H is to passivate the acceptors but H-donors themselves do not play a significant role. These acceptor-like defects are located at grain boundaries (dangling bonds) and in bulk (V-Zn and/or Ga-Zn-V-Zn). Post-growth annealing experiment and optical transmittance results exhibit that the passivated acceptors are mainly at grain boundaries rather than in bulk.