FERMI-LEVEL PINNING AT GAAS AQUEOUS AND N ON-AQUEOUS ELECTROLYTE JUNCTIONS/

In this paper, flatband potential measurements are used to study the F ermi Level Pinning (FLP) at the n or p-GaAs/aqueous and non aqueous el ectrolyte interface, The semiconductor is put in contact with an aqueo us solution containing the 18-tungsto-diphosphate P2W18O626- heteropol yanion as a redox system and with two non aqueous solutions : acetonit rile (ACN) and propylene carbonate (CP) in the presence of various red ox couples, Our results are firstly analyzed according to the classica l model proposed for solid-state semiconductor/metal junctions. A more specific model accounting for the coupling between corrosion and redo x reactions at the semiconductor/electrolyte interface is developped. The semiconductor surface equilibrates mainly with the redox species i n ACN solutions (total FLP), and only weakly in H2O or CP solutions, b ecause of the pre-eminence of the semiconductor/solvent interactions.