A COMPARISON OF INTENSITY-MODULATED PHOTOCURRENT SPECTROSCOPY AND PHOTOELECTROCHEMICAL IMPEDANCE SPECTROSCOPY IN A STUDY OF PHOTOELECTROCHEMICAL HYDROGEN EVOLUTION AT P-INP

A theoretical model describing the impedance of the illuminated semiconductor\electrolyte interface has been formulated within the same framework as that used to describe the photocurrent response of the interface to intensity modulated illumination. The analysis, which avoids the a priori assumption of an equivalent circuit to describe recombination and charge transfer, shows that intensity modulated photocurrent spectroscopy (IMPS) and photoelectrochemical impedance spectroscopy (PEIS) should provide the same information about the rate constants of charge transfer and recombination. An investigation of photoelectrochemical hydrogen evolution at p-InP has been performed using IMPS and PEIS. The rate constants of charge transfer and recombination derived by the two types of measurements agree within experimental error. Both rates depend on illumination intensity, and this is attributed to the multistep reaction mechanism involved in hydrogen evolution.