ELECTROCHEMICAL AND ETCHING BEHAVIOR OF INP SINGLE-CRYSTALS IN IODIC ACID-SOLUTIONS

The etch rate of the (100)-face of n- and p-type InP and that of the (111)- and (111BAR)-faces of n-InP in aqueous iodic acid solutions was measured as a function of several variables using a flow-cell setup. The electrochemical behavior of HIO3 at the n- and p-InP electrode was investigated cathodically and anodically, in darkness and under illumination. The limiting photocurrent, both cathodically for p-type as anodically for n-type InP, was found to be enhanced when adding HIO3 to the indifferent electrolyte solution; possible electrode reaction mechanisms are discussed. By combining the etch and electrochemical results, the stoichiometry of the etch reaction was deduced, and it was established that the etch process occurs by a chemical mechanism, involving the formation of radical-type decomposition intermediates. chemical etching was found to compete with anodic etching when holes are available at the surface. A difference in surface morphology after etching was observed between the (111)-face, on one hand, and the (111BAR)- and (100)-faces, on the other hand, although the etch rate was in all cases diffusion-limited. A tentative explanation for this phenomenon is proposed.