Electrochemical impedance spectroscopy at semiconductor electrodes: the recombination resistance revisited

Abstract

The correspondence between an electron-hole recombination step at the semiconductor electrode surface and the electrical impedance spectrum is reconsidered. It is shown theoretically that the well-known recombination resistance is identical to the faradaic resistance of a direct capture process. This fact is illustrated experimentally, using the reduction of methylviologen at n-GaAs as an example. A recombination-like resistance is hence not typical for hole injection steps in cathodic reduction reactions at n-type semiconductors. The consequences of this conclusion to the interpretation of electrical impedance spectra based on reaction models are discussed.