Abstract

Thin films of native oxides were anodically grown on n-type Hg_1−xCd_xTe (x = 0.2 and 0.3) to achieve surface passivation which is essential to the function of this narrow gap semiconductor as a high performance infrared detector. To establish a basis for correlation of the physical and chemical properties which arise from the formation of these films, we studied and identified the electrochemical reactions at the onset of anodization and analyzed the composition and structure of the resulting anodic films. For these analyses we employed angle-resolved and standard x-ray photoelectron spectroscopy in combination with electrochemical techniques, such as cyclic current-voltage measurements. We found that composition and structure of anodic films on Hg_1−xCd_xTe depend significantly on two growth parameters, namely, the electrolyte (pH 4.7–13) and the density of the anodic current (galvanostatic anodization). The native oxide films grown at pH 4.7 were found to be rich in Te and Hg, and HgTe₂O₅ was identified as a major oxide constituent. At pH 13, CdTeO₃ is the dominating native oxide; however, if the aqueous component of the electrolyte is partially replaced by ethylene glycol or a similar organic liquid, the solubility of the tellurite decreases, the HgTeO₃ precipitates at the electrolytic interface of the growing film and decisively improves the physical properties of the film.

© 1986 Optical Society of America