The properties of as-prepared and rapidly thermally oxidized Si1−x−yGexCy alloy films have been examined using infrared, X-ray diffraction, and Raman techniques. The structural properties of the oxidized Si1−x−yGexCy film depend on the type of strain of the as-prepared film. For compressive or fully compensated films, the oxidation process drastically reduces the carbon content such that the oxidized film compositions resemble that of Si1−xGex films. For tensile films, two broad layers co-exist in the oxidized films, one with a carbon content higher and the other lower than that required for full strain compensation.