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

Abstract

The frequency dependence of the semiconductor∣electrolyte interfacial capacitance may be simulated by a parallel connection of a capacitor—representing the semiconductor space-charge layer—and a constant-phase element. In this paper, we present an experimental impedance study of both n- and p-InP and n- and p-GaAs in H₂SO₄-containing solutions. It is shown that the frequency dependence of the interfacial capacitance is related to the conductivity of the electrolyte and to the pretreatment of the semiconductor surface. These experimental results enable a thorough discussion on the possible origins of the dispersion phenomenon. It is argued that frequency dispersion originates from localized states at the semiconductor surface, interacting with the electrolyte. From the experimental results, it follows that the surface states involved probably originate from surface damage, whereas surface roughness most likely determines the relation between dispersion and electrolyte conductivity.