Stress dependent properties of Ga-doped ZnO thin films prepared by magnetron sputtering

Ga doped ZnO films have been prepared by radio frequency magnetron sputtering at room temperature. The (002) preferential orientation is observed for all the films. In plane lattice parameters of the films are obtained by X-ray diffraction theta-2 theta scan with the samples tilted 61.63 degrees. Intrinsic compressive stress is observed parallel to the film surface, varying from 410 to 3,000 MPa. Electrical properties of the films show a great dependence on the stress. Carrier concentration and mobility are both improved as the intrinsic compressive stress is reduced which is greatly affected by adjusting the deposition pressure. Therefore, the electrical resistivity is optimized to be 1.8 x 10(-3) Omega.cm for the film prepared at 8.0 Pa. In addition, the optical analysis reveals that the transmittance of the films is higher than 90 %. The band gap of the films increases from 3.11 to 3.38 eV with decreasing the stress due to the increase in the carrier concentration, which is related to Burstein-Moss effect.