US Patent 7553690 Starved source diffusion for avalanche photodiode

This disclosure is concerned with starved source diffusion methods for forming avalanche photodiodes are provided for controlling an edge effect. In one example, a method for manufacturing an avalanche photodiode includes forming an absorber layer and an avalanche layer over a substrate. Next, a patterned mask defining one or more openings is formed over a surface of the avalanche layer. Finally, a dopant is deposited over the patterned mask and the avalanche layer such that the dopant is blocked by the patterned mask but diffuses into the avalanche layer in areas where the patterned mask defines an opening. The patterned mask is configured such that the depth to which the dopant diffuses into the avalanche layer varies so as to form a sloped diffusion front in the avalanche layer.