Patent ID: 7948018
Filing Date: 2011-05-24
Classification: H01L

Abstract:
1. An image sensor pixel, comprising: a substrate doped to have a first conductivity type; an epitaxial layer disposed over the substrate and doped to have a second conductivity type opposite of the first conductivity type; a light collection region for collecting photo-generated charge carriers disposed within the epitaxial layer, wherein the light collection region is doped to have the first conductivity type, wherein the light collection region is defined to be a doped region having only the first conductivity type; a buffer layer disposed between the epitaxial layer and the substrate, the buffer layer doped to have the first conductivity type; and a barrier layer disposed between the epitaxial layer and the buffer layer, the barrier layer doped to have the second conductivity type, the barrier layer having a higher dopant concentration than the epitaxial layer, wherein the buffer layer impedes diffusion of dopants of the first conductivity type from the substrate into the epitaxial layer, wherein the barrier layer generates an electric field that pushes charge carriers generated in the epitaxial layer towards the light collection region while impeding charge carriers generated in the buffer layer or the substrate from entering the epitaxial layer.