Patent ID: 7893464

Claim:
A semiconductor photodiode, comprising: a semiconductor substrate; a stack of layers on said substrate, including an absorption layer and a window layer on the top of the stack; wherein the window layer has a recess to a predetermined depth and lateral extent, and the recess has a lateral periphery; wherein the recess has a substantially flat portion, and a wall surrounding the recess runs smoothly and gradually from a level of the recess to a level of a surface of the window layer, so that in operation, the strength of an electric field adjacent to the wall is less than 200% of the strength of an electric field near and under the substantially flat portion of the recess; wherein the window layer is doped so as to form a doped sub-layer therein, and the doped sub-layer forms, in the recess of the window layer, a p-n junction at a boundary with a next layer in the stack, and wherein said p-n junction defines a photosensitive area of the photodiode; and a first electrical isolation region surrounding the periphery of the recess, wherein said first electrical isolation region is formed by ion implantation or wet oxidation and is buried underneath the doped sub-layer, so as to confine a flow of electric current to the p-n junction.