PHOTODIODES WITH SERPENTINE SHAPED ELECTRICAL JUNCTION

A photodiode comprising: a substrate having an upper surface; a first well of a first conductivity type in the substrate; and a second well of a second conductivity type in the substrate, the second conductivity type is of an opposite conductivity type to the first conductivity type, the second well is above and in direct contact with the first well, the second well comprises: a central section having a bottom with a first depth relative to the upper surface of the substrate; and a first concentric section laterally surrounding the central section, the first concentric section having a bottom with a second depth relative to the upper surface of the substrate, wherein the second depth is different from the first depth.