The nature of,electron tunneling through self-assembled monolayer films on n-InP semiconductor electrodes is explored. The photocurrent of a semiconductor cell is measured as a function of the thickness of an alkanethiol overlayer film. This work reports a detailed investigation into the photocurrent and its dependence on control parameters of the photoelectrochemical cell. This study demonstrates that the study of the photocurrent versus chain length of the alkanethiol can be used to examine how the electron-transfer rate constant depends on the thickness of the insulating layer-of particular interest is the ability to probe the distance dependence of the electronic coupling.