We have used spectroscopic ellipsometry to determine the complex dielectric function from 1.5 to 6.0 eV for Hg0.71Cd0.29Te and some of its native oxides. The electrochemically grown anodic oxide was found to have an absorption threshold near 3 eV and its dielectric function shows some of the features of TeO2. We found no evidence for a Tehyphen;rich layer between the native oxide and the semiconductor. However, after stripping the oxide with HCl, a residual layer with Tehyphen;like optical and chemical properties did appear. Thin native oxides formed by exposure to ozonehyphen;containing oxygen had dielectric functions similar to that of the anodic oxide but with a broader absorption edge. These oxides could be stripped partly by water and totally by HCl. This confirms that they are a mixture of several oxides as also concluded in other investigations. We found no evidence for any disorder or defects induced in HgCdTe by anodization or etching.
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