Lateral resistance of silicon-based p-type and n-type Schottky junctions is investigated. After one electrode on a metallic film is irradiated, the differential lateral resistance of the system is dependent on the direction of the bias current:it keeps constant in one direction and decreases in the opposite direction. By systematically investigating the electrical potential changes in silicon and the junction, we propose a new mechanism based on light-controlled leak current. Our work provides an insight into the nature of this phenomenon and will facilitate the advanced design of switchable devices.