Patent ID: 7348608

Claim:
A planar avalanche photodiode comprising: a first semiconductor layer; a first contact layer, the first contact layer being on the first semiconductor layer; a second contact layer defining a small local contact; a second semiconductor layer with a diffusion region, the second semiconductor layer being undoped or low doped; the diffusion region having a smaller area than the second semiconductor layer and being positioned adjacent to the second contact layer, whereby the diffusion region creates a contact region between the diffusion region and the second semiconductor layer; a semiconductor multiplication layer positioned between the first and second semiconductor layers, whereby the semiconductor multiplication layer multiplies a generated carrier; a semiconductor absorption layer positioned between the semiconductor multiplication layer and the second semiconductor layer, the semiconductor absorption layer absorbs light, generating the carrier; a charge control layer, the charge control layer being located between the semiconductor absorbtion layer and the semiconductor multiplication layer, the charge control layer having a substantially uniform thickness and an area larger than the diffusion region; and at least one grading layer positioned adjacent to the semiconductor absorption layer.