The photocurrent density j(Ph) and the excess microwave reflectivity, Delta R-M, at the semiconductor/electrolyte boundary are calculated using analytical expressions for the excess minority carrier profiles. The model incorporates diffusive terms in the space charge region, depending on the surface parameter values, K-r (charge transfer velocity), and S-r (surface recombination velocity), the influence of small electrical fields in the so-called neutral region and the back contact recombination velocity, S-rb. Photocurrent-voltage and excess microwave reflectivity-voltage curves are calculated depending on K-r and S-r showing that it is possible to determine these surface kinetic parameters from simultaneous measurements of j(Ph) and Delta R-M. It is shown that for cases in which the quantum yield is high, microwave measurements exhibit a higher-sensitivity to changes in experimental parameters.