A method has been developed to use the scanning tunneling microscope (STM) for local photocurrent measurements on semiconductor surfaces, especially under short circuit conditions. The topographical image of the surface is obtained together with the local size of photocurrent simultaneously. Measurements have been performed on surfaces of n- and p-type WSe2 monocrystals in air. Defect sites show up in the photocurrent image due to their strong local recombination. The electrical properties of the contact between the tunneling tip and the semiconductor surface have been analyzed here in detail. They can be understood as a classical Schottky diode. Photocurrent measurements have been used to analyze the local electrical properties of the surface and a quantitative analysis of the electrical properties has been performed on the basis of local current-voltage curves. Besides clean surfaces, those modified with metal particles have also been investigated.