Effects of Ga Doping and Substrate Temperature on Electrical Properties of ZnO Transparent Conducting Films Grown by Plasma-Assisted Deposition

Transparent conducting ZnO films are deposited by plasma-assisted deposition on glass and plastic substrates at temperatures as low as 50 °C. The effects of Ga doping and growth temperature on electrical properties are studied using Hall measurement and X-ray diffraction. Carrier density increases with Ga doping for both 50 and 300 °C growth. For low-temperature growth, the carrier mobility in undoped ZnO films is the same as that in high-temperature-grown films, but it becomes lower as the Ga doping level becomes higher. Lattice expansion in both $c$ and $a$ axes directions is observed for low-temperature-grown highly Ga-doped films. The relation between the mobility reduction and the lattice expansion is discussed.