CHARGE-TRANSFER AND STABILIZATION AT ILLUMINATED N-GAAS AQUEOUS-ELECTROLYTE JUNCTIONS

A simple model for the charge transfer process at various n-GaAs/aqueous electrolyte junctions is proposed. The assumptions made in the model are justified thanks to Electrochemical Photocapacitance Spectroscopy experiments; this technique is of great help in such a matter. As a result, the model accounts very well for the numerous aqueous electrolytes we used. It is found that (i) the more reducing the redox couple the greater the kinetics, ie S increases (ii) the more concentrated the redox species the more stabilized the electrode and (iii) the smaller the water concentration the greater S. All the parameters of the model are discussed and physically interpreted. The main results are: (i) the direct transfer for the redox reaction and (ii) the greater S the more pinned at the surface the band edges of the semiconductor.