Analysis of photoluminescence experiments onp-type GaAs electrodes using a drift-diffusion model

We report an analysis of time-resolved photoluminescence from capped p-type GaAs in contact with solutions of cobaltocenium in acetonitrile in the presence of an externally applied potential. We use a drift-diffusion model to describe the dynamics of carriers in the semiconductor. We compare the results to experimental measurements which might qualitatively suggest a rapid electron-transfer rate from the GaAs to cobaltocenium ions in solution. The results show, however, that the experimentally observed decay in the photoluminesce is dominated by the charge separation produced by the electric field, and the computed values of the electron-transfer velocity $S_{\mathrm{et}}$ are quite small. The resulting $S_{\mathrm{et}}$ is shown to have a slight dependence on the external potential. This potential dependence is not significant enough to be definitively established by the procedures described here. We discuss the usefulness of these methods to establish the existence of the injection of hot carriers into an electrolyte.