Sheet resistance and crystallinity of Ga- and Al-implanted zinc oxide thin films with postannealing

Ion implantation experiments of Ga and Al into sputter-deposited ZnO films were carried out to control the resistivity to form n+-ZnO layers for device fabrication. The difference would be suitable for fabricating source and drain regions of ZnO thin film transistors. Improvement of ZnO crystallinity after the ion implantation was found by x-ray diffraction spectra and a thin film as shift of lattice parameter, enhancement of peak intensity, and a decrease of full width at half maximum in 2θ. The improvement of Ga-implanted ZnO was better than that of the Al-implanted ZnO throughout the experiment. Difference in sheet resistance for seven orders of magnitude between unimplanted ZnO thin film and Ga-implanted ZnO was observed with postannealing at 300°C. The sheet resistance of the ZnO film was decreased to 3.4×102Ω∕◻ with a postimplantation annealing at 450°C.