The effect of Ga doping on ZnO thin films subjected to CO2 laser annealing

Abstract

The effect of Ga dopant on ZnO thin films was studied for transparent conducting oxide (TCO) applications. In and Ga were selected as dopants for the ZnO thin films, and their mole ratios were varied to identify the optimum proportions of the two dopants. After doping, optical post-annealing processes were applied to improve the conducting properties of the films. By applying optical post-annealing processes, rapid thermal annealing and CO2 laser annealing, the dopants were ionized and thus contributed to the conducting process. The crystal and electrical properties were studied and analyzed. By determining the films’ absorption and transmittance properties, their energy band gaps were calculated, and through X-ray photoelectron spectroscopy analysis, we found that the Ga dopant plays an important role in the TCO behavior. The Ga dopant in the ZnO thin films that had undergone laser annealing improved the electrical conductance properties due to their contributing the oxygen vacancy concentration, increasing the amount of free electrons in the ZnO structure.