A 3-D electron-beam-induced current (EBIC) model was implemented in technology computer aided design simulations. The model uses a carefully designed charge carrier generation profile that describes how an electron beam induces charge carriers in a semiconducting device and then drift-diffusion equations are solved to determine the resulting current. The simulation provides a map of the EBIC signal, which can be compared with experimental 2-D profiles. This comparison can be used to fit parameters such as the surface recombination rate which is otherwise difficult to fit in completed devices. Additional experimental data for these fits are obtained by performing the experiments at different electron beam energies and thereby generating carriers at different depths in the sample. The experiments were performed on cross sections of silicon photodiodes with varying surface preparations. A strong influence of the surface preparation method on the charge carrier diffusion was observed.