Optical and electrical properties of p-type transparent conducting Cu-Al-O thin films prepared by plasma enhanced chemical vapor deposition

The growth of p-type transparent conducting oxide thin film has attracted much attention due to its potential in making novel transparent p–n junctions for device applications. In this work, the transparent conducting Cu–Al–O thin films were prepared by plasma enhanced chemical vapor deposition using metal organic precursors of Cu(acac)₂ and Al(acac)₃ (acac=acetylacetonate) in a mole ratio of 1:1 sublimated at 150°C. The metal organic vapor was carried into a reaction chamber by argon gas. Reactive oxygen gas was introduced into the chamber via another gas inlet. Substrate temperatures were varied over the range 630–800°C and the processing pressure was kept constant at about 0.15 Torr. Seebeck effect measurements revealed that these films were p-type semiconductors. X-ray diffraction results showed that Cu–Al–O films were amorphous. The resistivity mechanism of the low resistivity of Cu–Al–O films is probably governed by the scattering of the dominant hole-carriers by impurities. The film conductivity increased with increasing growth temperature. The films prepared at 800°C with a resistivity of 5.0 Ω·cm and transparency of over 60% in the visible light region were achieved.