A method for forming a back-illuminated image sensor includes forming a higher doped crystalline layer on a crystalline substrate, growing a lower doped crystalline layer on the higher doped crystalline layer and forming a photodiode and component circuitry from the lower doped crystalline layer. Metallization structures are formed to make connections to and between components. The crystalline substrate is removed to expose the higher doped crystalline layer. An optical component structure is provided on an exposed surface of the higher doped crystalline layer to receive light therein such that the higher doped crystalline layer provides a passivation layer for the photodiode and the component circuitry.