Photodiode arrays and methods of fabrication are provided. One photodiode array includes a silicon wafer having a first surface and an opposite second surface and a plurality of conductive vias through the silicon wafer. The photodiode array further includes a patterned doped epitaxial layer on the first surface, wherein the patterned doped epitaxial layer and the substrate form a plurality of diode junctions. A patterned etching defines an array of the diode junctions.