Photodiodes Come With Contacts On The Same Face

Flip-chip photodiodes have been developed that have both contacts on the same face. This allows the photodiode to have a front face without bond wires or other contact areas. Filters on either glass substrates or directly evaporated onto the photodiode active area are possible. Two-dimensional custom arrays can be made using this chip structure and contacts can be solder type or the wafer can be bumped to suit the application. The process uses aluminum, which is migrated from the front face of the device through a controlled temperature gradient. The front contact is then brought to the rear face by a conductive channel of p-type material. The technology is currently available for 4", n-type silicon wafers with a resistance range of up to 50 ohms/cm.