Basic electrochemical processes at GaAs, GaAsP, and GaA1As electrodes were studied in H~O~ aqueous solutions at several pH values. An analytical automatic system, which directly plots gallium concentration vs. potential, allows the collection of information on corrosion processes. The approach of making continuous analysis of gallium ions, while dissolving the semiconductor at a preselected potential, was used in conjunction with impedance and ellipsometric measurements in order to study interfacial phenomena. On the basis of these results, a mechanism for chemical corrosion (etching) which involves electrons captured from semiconductor surface states by H202 was proposed. Anodic polarization can also induce corrosion by hole generation in the valence band or by avalanche breakdown. As expected, pH plays a fundamental role in the corrosion process through the solubility shift of the oxide layer. Further consideration is given to the effect of illumination, with special emphasis on p-type semiconductors, for which it can lead to an inhibition effect on corrosion via a current doubling mechanism. Finally, application of selective etching is described for GaAs, GaA1As, and GaAsP hetero structures.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 141.211.4.224 Downloaded on 2015-06-13 to IP ABSTRACT The catalytic activity for electrooxidation of hypophosphite and electroless nickel plating on iron, nickel, and electrolessly plated nickel (with 2.2-2.9 weight percent (w/o) p) was investigated in an ammoniacal solution ofpH 8.8 at 50~ by potential measurements and linear sweep voltammetry from -0.3V to 0.92Vvs. SCE. Cathodic polarization of any of the substrates (in 0.1M H2SO4) before testing or permeation of hydrogen throughiron foils during testing reduced the incuba-

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A new electroless plating bath for the formation of In:Au alloy deposits is described. Like Okinaka's gold plating bath, it contains potassium borohydride as the reducing agent but EDTA must be added to cyanide ions in order to stabilize In3+. This bath can operate at room temperature, as proved by deposits obtained on Pd‐activated normaln‐normalGaAs substrates, at the price of a low deposition rate (0.1 μm h−1). As expected, better ohmic contacts were obtained by annealing heterostructures prepared by using In: Au (4:96) electroless deposits instead of the pure electroless gold.