Electron Trap Level of Cu-Doped ZnO

The electron trap level of Cu-doped ZnO has been investigated. Films with Cu contents from 0.01 to 1 at. % were deposited by RF magnetron sputtering onto (0001)-oriented sapphire substrates at 300 °C, and annealed at 900 °C. The resistivity of these films was high and increased with increasing Cu content. Hall measurements carried out at high temperatures of approximately 400 °C showed exponential temperature dependence. The results were analyzed assuming that donors and electron traps coexist. The electron trap energy level was determined to be in the 0.30–0.35 eV range below the conduction band edge.