A substrate section that is at least partially fabricated to include contact elements and materials. The substrate section includes doped regions that have a heavily doped N-type region and a heavily doped P-type region adjacent to one another. An exterior surface of the substrate has a topography that includes a light-transparent region in which light, from a light source, is able to reach a surface of the substrate. An application of light onto the light transparent region is sufficient to cause a voltage potential to form across a junction of the heavily doped regions. The substrate section may further comprise one or more electrical contacts, positioned on the substrate section to conduct current, resulting from the voltage potential created with application of light onto the light transparent region, to a circuit on the semiconductor substrate.