Abstract The electrochemical and chemical reactions of BrO − at GaAs in alkaline solutions, studied in this work, show a strong resemblance to results previously reported for alkaline ClO − and acidic Br 2 and H 2 O 2 systems. Common features of all these systems include cathodic reduction via a current doubling mechanism and a coupled chemical etching by the oxidizing agent. Recombination impedance measurements lead to the conclusion that the unified model involving a common precursor for etching and reduction reactions, proposed for symmetrical oxidizing agents, can also be applied to the asymmetrical agents ClO − and BrO − .