Crystallinity and resistivity of ZnO thin films with indium implantation and postannealing

Ion implantation experiments of indium (In) into sputter-deposited undoped ZnO films were carried out to control the resistivity for n+-ZnO layers of electronic device. Improvement of ZnO crystallinity after the ion implantation was revealed by x-ray diffraction patterns including a shift of lattice parameter, enhancement of peak intensity, and a decrease in full width at half maximum in 2θ. In-implanted ZnO crystallinity was greatly improved compared to results of the Ga and Al-implanted ZnO experiments. The resistivity of 1×1016ions∕cm2 implanted ZnO film was decreased with over 11 orders of magnitude to 5.1×10−2Ωcm with postimplantation annealing at 400°C. The ratio of resistivity between unimplanted ZnO and In-implanted one at 1×1015ions∕cm2 was seven orders of magnitude after annealing at 300°C. The In-implanted ZnO would be suitable for fabricating source and drain regions of ZnO thin film transistors.