Embodiments of a process comprising forming a pixel on a front side of a substrate, thinning the substrate, depositing a doped silicon layer on a backside of the thinned substrate, and diffusing a dopant from the doped silicon layer into the substrate. Embodiments of an apparatus comprising a pixel formed on a front side of a thinned substrate, a doped silicon layer formed on a backside of the thinned substrate, and a region in the thinned substrate, and near the backside, where a dopant has diffused from the doped silicon layer into the thinned substrate. Other embodiments are disclosed and claimed.