Abstract: In this paper the transient behaviors of n-InP in Fe³⁺/Fe²⁺ solution are studied using pulsed light technique. The effects of load resistance and Fe²⁺ concentration on the response are observed.From the peak position of the response it can be regarded that the electrode is in the pseudo-stable state at the peak because the production and the separation of photo- indused carriers are very fast. The peak current increases with decreasing load resistance and increasing the concentration of ferrous ion. It agrees with the output characteristic of general cell.The decay process of the response can be explained by a RC equivalent circuit and follows the law of dual-exponential.The time constants increase linearly with increasing the load resistance. From the slope of the lines the capacities of the space charge layer and the surface states can be calculated. In-creaing the concentration of ferrous ion decrease the time constants.

Key words: photoelectrochemistry, indium phosphide