Patent ID: 7851823

Claim:
A semiconductor photodetector device comprising: an n-type first semiconductor layer; a first absorption layer having a bandgap energy; a second semiconductor layer having a bandgap energy larger than the bandgap energy of said first absorption layer and including a p-type doped region located at a surface of said second semiconductor layer; a second absorption layer located between said first semiconductor layer and said first absorption layer; an electric field reduction layer located between said first absorption layer and said second absorption layer; and a multiplication layer located between said first absorption layer and said second absorption layer, wherein said first semiconductor layer, said second absorption layer, said multiplication layer, said electric field reduction layer, said first absorption layer, and said second semiconductor layer are arranged from bottom to top, in that order, in a laminated structure, so that said second semiconductor layer is separated from said multiplication layer by at least said first absorption layer, and said second absorption layer, in response to incident light, injects electrons into said multiplication layer, and said semiconductor photodetector device detects light incident on the surface of said second semiconductor layer.