Silicon Sensor has developed a process to produce flip-chip photodiodes with both contacts on the same face, allowing them to have a front face without bond wires or other contact areas. Aluminum is migrated from the front face under a controlled temperature gradient, and brought to the rear face by a conductive channel of P-type material. It is possible to put filters on glass substrates or evaporate them onto the photodiode's active area. The technology is available for 4-in. N-type silicon wafers with a resistivity up to 50 (omega).