The solubility of nitrogen in ZnO films grown at various temperatures by metal-organic chemical vapor deposition, using NO as both oxygen and nitrogen sources, was investigated. ZnO films were grown at 270, 310 and 370C, and subsequently annealed in oxygen at 700 or 850C. In addition to nitrogen, hydrogen and carbon were also present in the samples. The presence of these impurities was partially explained by the formation of complexes such as (CN)O and CHx (x = 1, 2, 3). Post-growth annealing performed on the samples suggested that the out-diffusion of such complexes was strongly influenced by the crystallinity of the films. The high porosity of films grown at temperatures ≤310C was favorable for the diffusion of the complexes, which resulted in a more efficient thermal activation of nitrogen acceptors in ZnO:N.

Effect of the Crystallinity of MOCVD-Grown ZnO:N on the Diffusion of Impurities. Dangbégnon, J.K., Talla, K., Vines, L., Botha, J.R.: Journal of Crystal Growth, 2011, 324[1], 243-7