Electrochemical behaviour of (1 0 0) GaAs in copper(II)-containing solutions

Abstract

The electrodeposition of copper from acidic chloride and sulfate solutions onto the surface of n- and p-GaAs electrodes and the dissolution of copper from the GaAs surface have been studied by means of cyclic voltammetry, rotating-ring-disk voltammetry and impedance measurements. The results show, that the reduction of Cu 2+ is due to the injection of holes. In chloride solutions, reduction to Cu + precedes the reduction to Cu 0, whereas in sulfate solutions no Cu + intermediates are detected. At open-circuit potential, Cu 2+ is reduced to Cu + in chloride solutions, Cu 2+ hence being an electroless etchant for GaAs. At p-GaAs, dissolution of copper by holes is observed both in Cl − and SO 4 2− medium, whereas at n-GaAs in chloride solutions, copper is seen to dissolve chemically. Mechanisms explaining the observed potential-dependence of the hole injection rate are proposed, and the morphology of the copper layers as well as the electrical properties of the resulting GaAs/Cu dry junctions are discussed.