Anodic and Electroless Etching of Germanium in Alkaline Hexacyanoferrate Solutions

This paper presents results of a study on the electrochemical and etching behavior of Ge in alkaline hexacyanoferrate solutions. A detailed analysis of the current-potential behavior in these solutions allowed important conclusions to be drawn concerning the anodic dissolution mechanism of Ge. It was found that some oxidation steps involve mobile dissolution intermediates instead of, as generally accepted, free holes. Moreover, the electrochemical experiments indicate that hexacyanoferrate etches Ge according to an electroless mechanism, which was confirmed by etching experiments at open-circuit potential. Reproducible etch rates were obtained and only slight surface roughening after etching was observed.