Patent ID: 8022495

Claim:
A PIN photodiode comprising: a substrate; a first-type semiconductor contact layer on the substrate; a first layer over the first-type semiconductor contact layer, the first layer comprising a first region of intrinsic material and a second region dopant, wherein the intrinsic material has a small, residual carrier concentration of the first type, and wherein the second region is doped second type and forms a PN junction with the first region; a second layer over the first layer, the second layer comprising a first type window layer and a second type window layer to form a PN junction with the first type window layer; a third layer over the second layer, the third layer comprising an aperture, a first inner ring portion, and a second outer ring portion circumferentially surrounding the aperture, wherein the second outer ring portion is thinner than the first inner ring portion and intrinsic material in the second outer ring portion is depleted; and a contact electrode over the second type window layer.