On the electrochemical impedance of InP and GaAs electrodes in indifferentelectrolyte. Part 2. Experimental study on the factors influencing the frequency dispersion

The frequency dependence of the semiconductor/electrolyte interfacial capac itance may be simulated by a parallel connection of a capacitor-representin g the semiconductor space-charge layer-and a constant-phase element. In thi s paper, we present an experimental impedance study of both n- and p-InP an d n- and p-GaAs in H2SO4-containing solutions. It is shown that the frequen cy dependence of the interfacial capacitance is related to the conductivity of the electrolyte and to the pretreatment of the semiconductor surface. T hese experimental results enable a thorough discussion on the possible orig ins of the dispersion phenomenon. It is argued that frequency dispersion or iginates from localized states at the semiconductor surface, interacting wi th the electrolyte. From the experimental results, it follows that the surf ace states involved probably originate from surface damage, whereas surface roughness most likely determines the relation between dispersion and elect rolyte conductivity.