Transparent conducting Zn1−xMgxO:(Al,In) thin films

Zn1−xMgxO:Al thin films have been grown epitaxially on c-plane sapphire substrates by direct current reactive magnetron sputtering. Structural evaluation indicated that the ZnMgO films had similar crystalline perfection as ZnO films grown under similar conditions. Postdeposition annealing with in situ In doping was done at 415 °C for 4 h in H2/Ar mixtures, resulting in improved electrical properties. Increasing the Mg content from 0 to 20 at. % increased the band gap but decreased the conductivity, mobility, and electron density in annealed films. The decrease in mobility was explained by a combination of increasing electron effective mass and alloy disorder scattering. Increasing the Al dopant content in ZnMgO had similar effects as in pure ZnO, increasing the carrier density and optical band gap but decreasing the mobility. Band gaps of 3.76 eV were achieved in the Zn0.8Mg0.2O:(Al,In) films with a corresponding resistivity of 2×10−2 Ω cm, a carrier concentration of 4×1019 cm−3, and a mobility of 7 cm2/V s.

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