The segregation of native defects and Bi impurities to a high-angle grain boundary was studied by means of first-principles calculations. It was found that the presenceof BiZn increased the concentration of native defects of acceptor type in the grain boundary. This led to the formation of a BiZn + VZn + Oi interfacial complex under O-rich conditions and a localized acceptor state. This state, which was different to that of the isolated impurity, gave the grain boundary a p-type character and, when embedded between n-type ZnO grains, was consistent with the double Schottky barrier model for Bi-doped ZnO.

An Interfacial Complex in ZnO and Its Influence on Charge Transport. Carlsson, J.M., Domingos, H.S., Bristowe, P.D., Hellsing, B.: Physical Review Letters, 2003, 91[16], 165506