| Cadmium Oxide (CdO) is a direct wide bandgap semiconductor material with the bandgap of about 2.3eV. CdO is widely used as transparent condcting electrode, heating-reflecting mirrors for glass windows and gas sensor, etc, because of its unique properties: high carrier concentration, high mobility, high transmittance and low synthesized temperature. The bandgap of CdO film 2.3eV is fit with visible spectrum region of solar radiation, so CdO films can be used as solar cell window material with CdTe, CuInSe2, and Si, instead of tranditional CdS.In this paper, the various properties, applications, growth techniques of CdO films and progresses in the research of CdO were reviewed. And CdO films were synthesized on glass substrates by thermal oxidation of metallic Cd films and DC reactive magnetron sputtering. In order to improve the conductivity and transmittance of CdO film, Aluminum doped CdO films (AlxCd1-xO) were fabricated using DC reactive magnetron sputtering.Then the properties of the CdO and AlxCd1-xO films, and the effects of growth parameters on quality of CdO films were studied. Results show that: 1) The properties of CdO films by DC reactive magnetron sputtering are better than those by thermal oxidation. The lowest resisitivity of 1.98×10-4Ωcm was obtained at the optimal parameter (O2 flow rate: 20sccm, substrate temperature: 200℃). 2) The carrier concentration increases when the aluminum concentration x increases from 0.425at% to 3.4at%, and the lowest resistivity was obtained when x=3.4at%. The absorption edge shifts to shorter wavelengths as x increases, and the transmittance of the AlxCd1-xO film in the range of 550nm-700nm is improved when Al is doped. 3) Compared to pure CdO, the resistiviry of AlxCd1-xO is not improved too much as expected, but the transmittance in the range of 500nm-700nm is increased.
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