Electroreduction of Co2+ and Ni2+ at III-V semiconductors and properties of the semiconductor/metal interfaces formed

The electrochemical deposition of Ni and Co on GaAs and GaP at pH 5 was inv estigated by means of cyclic voltammetry and rotating disk voltammetry. The current-potential behavior of the two semiconductors in dilute metal ion s olutions appeared to he different: at n-GaP, a stepwise reduction of the me tal ions was observed whereas at n-GaAs this was not the case This observat ion can be explained on the basis of two alternative reaction mechanisms fo r the reduction of the monovalent intermediate. Under well-chosen condition s of deposition potential and metal ion concentration, it appeared to he po ssible to form adherent n-GaAs/Co, n-GaAs/Ni, and n-GaP/Co Schottky contact s with good rectifying properties. The barrier height Phi(B) of the n-GaAs/ Ni contacts appeared to increase as a function of time, leading to values o f Phi(B) which were dependent on the deposition potential V-D. At n-GaAs/Co and n-GaP/Co junctions, this aging effect was absent, leading to values of the barrier height which were independent of V-D. It was further observed that the occurrence of side reactions during metal deposition may exert a g reat influence upon the properties of the metal/semiconductor junctions for med. (C) 1999 The Electrochemical Society. S0013-4651(98)07-026-8. All righ ts reserved.