US Patent 7592651 Low dark current photodiode for imaging

A photodiode and method of forming a photodiode has a substrate. An absorption layer is formed on the substrate to absorb lightwaves of a desired frequency range. A multiplication structure is formed on the absorption layer. The multiplication layer uses a low dark current avalanching material. The absorption layer and the multiplication layer are formed into at least one mesa having in an inverted “T” configuration to reduce junction area between the absorption layer and the multiplication layer. A dielectric layer is formed over the at least one mesa. At least one contact is formed on the dielectric layer and coupled to the at least one mesa.