Transport properties of phosphorus-doped ZnO thin films

The doping behavior of phosphorus in ZnO thin films grown by pulsed laser deposition is examined. The transport properties of epitaxial ZnO films doped with 1-5 at. % P were characterized via room temperature Hall measurements. As-deposited films doped with phosphorus are highly conductive and n type. The origin of the shallow donor level appears to be either substitution of P on the Zn site or formation of a donor complex. Annealing these phosphorus-doped films significantly reduces the carrier density, transforming the transport from highly conducting to semi-insulating. These results indicate that the phosphorus-related donor defect is relatively unstable, and suggests the formation of a deep level upon annealing. The latter is consistent with phosphorus substitution on the O site yielding a deep level in the gap. (C) 2003 American Institute of Physics.