Electrodissolution and passivation phenomena in III–V semiconducting compounds

Abstract

Anodic dissolution and passivation characteristics of n- and p-type III-V compounds (III=Ga, In and V=P, As, Sb) have been compared in aqueous electrolytes. A range of interfacial behavior was observed on controlled potential cycling of these semiconductors in acidic, basic, and neutral solutions, the differences being more pronounced in acids. The dissolution of InP on anodization is severely inhibited even in acid medium by the formation of a coherent film removable only by extensive cathodic reduction. GaP, InSb, and GaSb passivate less readily, forming solubility-limited precipitates on the surface at high current densities. Passivation of InAs or GaAs at pH∼0 is virtually unreachable, except at extremes of current densities, with the films formed being quite porous and permitting considerable surface corrosion. The gradation of properties observed in the III–V compound series indicates that both group III and V members are involved in the film formation. Previous observations of the functions of films on InP and GaAs in photoelectrochemical cells, in acid and neutral media, respectively, are consistent with the above results. The formation of indium layers in InP, after reduction in acid media, has been demonstrated by ring–disk electrode techniques.