Post-growth annealing induced change of conductivity in As-doped ZnO grown by radio frequency magnetron sputtering

Arsenic-doped ZnO films were fabricated by radio frequency magnetron sputtering method at a relatively low substrate temperature of 200 degrees C. Post-growth annealing in air was carried out up to a temperature of 1000 degrees C. The samples were characterized by Hall measurement, positron annihilation spectroscopy (PAS), secondary ion mass spectroscopy (SIMS), and cathodoluminescence (CL). The as-grown sample was of n-type and it converted to p-type material after the 400 degrees C annealing. The resulting hole concentration was found to increase with annealing temperature and reached a maximum of 6 x 10(17) cm(-3) at the annealing temperature of 600 degrees C. The origin of the p-type conductivity was consistent with the As-Zn(V-Zn)(2) shallow acceptor model. Further increasing the annealing temperature would decrease the hole concentration of the samples finally converted the sample back to n-type. With evidence, it was suggested that the removal of the p-type conductivity was due to the dissociation of the As-Zn(V-Zn)(2) acceptor and the creation of the deep level defect giving rise to the green luminescence. (C) 2011 American Institute of Physics. [doi:10.1063/1.3665713]