Enhanced Electrical Mobilities of Laser Annealed Ga Doped ZnO Thin Films

In this study, Ga-doped ZnO thin films were prepared, and their potential for transparent conducting oxide applications was assessed. To increase the electrical mobility and reduce the resistance of Ga-doped ZnO thin films, CO₂ laser annealing was employed. Recently, the use of transparent conducting oxides (TCOs) have increased, particularly ZnO-based TCOs have been intensively investigated for display applications. To enhance the electrical and optical properties of ZnO thin films, Ga was used as a dopant. First, Ga-doped ZnO thin-film precursors were prepared by the sol-gel method. Subsequently, Ga-doped ZnO thin films were coated on glass substrates by spin coating. Electrical furnace treatment and rapid thermal annealing were employed to obtain and anneal a wurtzite ZnO based structure. The electrical and optical properties of the annealed thin films were optimized by varying the Ga doping concentration. Via Ga doping and optimized laser annealing, the resistivity of the ZnO film could be decreased from 16.32 Ω· cm to 0.45 Ω·cm; notably, the transmittance was similar (85%) in the 380-800 nm range. The transmittance properties of the films are not presented in this paper. Moreover, after an optical CO₂ laser annealing process, the conductivity of the films improved by more than 40 times. Furthermore, the electrical properties (mobility, resistivity, and bulk and sheet concentrations) of the CO₂-laser-annealed Ga-doped ZnO thin films were optimized.