Patent ID: 8704272

Claim:
An avalanche photodiode, comprising: a substrate; and a multi-layer structure disposed on the substrate, the multi-layer structure comprising: a first contact layer coupled to at least one metal contact of a first electrical polarity; an absorption layer on which the first contact layer is disposed, the absorption layer absorbing photons of an optical beam incident on the multi-layer structure; an electric field control layer on which the absorption layer is disposed; a multiplication layer on which the electric field control layer is disposed, the multiplication layer configured such that an avalanche breakdown occurs in the multiplication layer in response to the absorption layer absorbing the photons of the optical beam; and a second contact layer on which the multiplication layer is disposed, the second contact layer coupled to at least one metal contact of a second electrical polarity, wherein: the absorption layer is made of a first material; the electric field control layer is made of a second material and aids distribution of an electric field inside the multiplication layer; a central region of the electric field control layer is doped with a first type of dopant at a first level of concentration and a circumferential region of the electric field control layer surrounding the central region is doped with the first type of dopant at a second level of concentration higher than the first level; and wherein a portion of the central region of the multiplication layer is doped with a second type of dopant, and wherein one or more of a size, a doping concentration, and a thickness of the central region of the multiplication layer are controlled so that an electric field in the central region is higher than that of regions of the multiplication layer that surround the central region.