Hydrogen-doped high conductivity ZnO films deposited by radio-frequency magnetron sputtering

Hydrogen-doped zinc oxide (ZnO: H ) films were deposited by rf magnetron sputtering as transparent conductive films. The resistivity of ZnO: H film was significantly reduced by the addition of H 2 in Ar during rf sputtering. The electrical resistivity of ZnO: H films reached 2 × 10 − 4 Ω cm . The carrier concentration increased with increasing H 2 concentration during deposition. X-ray diffraction results showed that the d 0002 interplanar spacing increased with increasing H 2 concentrations. The carrier concentration was significantly reduced in two orders of magnitude by increasing the substrate temperature from 150 to 250°C during deposition. Both results suggested that the increase of carrier concentration by adding H 2 during sputtering was due to the hydrogen donor rather than the oxygen vacancies in ZnO films, consistent with the theoretical predictions by Van de Walle. UV-visible spectroscopy further showed that the transmittance is high up to 100% in the visible range. The band gap determined by optical absorption increased with increasing H 2 composition. The phenomenon is interpreted as the filling of conduction band by electrons in n -type semiconductor.