A backside illuminated image sensor comprises a sensor layer implementing a plurality of photosensitive elements of a pixel array, and an oxide layer adjacent a backside surface of the sensor layer. The sensor layer comprises a seed layer and an epitaxial layer formed over the seed layer, with the seed layer having a cross-sectional doping profile in which a designated dopant is substantially confined to a pixel array area of the sensor layer. The doping profile advantageously reduces dark current generated at an interface between the sensor layer and the oxide layer. The image sensor may be implemented in a digital camera or other type of digital imaging device.