The Influence of Surface Recombination and Trapping on the Cathodic Photocurrent at p‐Type III‐V Electrodes

The factors contributing to the large overpotential with respect to flatband potential required for hydrogen evolution and certain redox reactions at illuminated p‐type electrodes of various III–V compounds have been investigated. Results of photoelectrochemical studies, involving minority carrier transfer to redox systems in the electrolyte, indicate that surface states acting as recombination centers are important. Thin‐slice measurements with a p‐n junction show that the recombination velocity at the interface is indeed very high, even at potentials corresponding to a thick depletion region. Results of impedance measurements made with illuminated electrodes emphasize the importance of charge localization in surface states. A model based on surface recombination and electron trapping can explain the photocurrent‐potential and impedance characteristics of the p‐type electrodes.