Photo sensing device and method of fabricating the photo sensing device

A photo sensing device, comprising:

• a substrate, comprising a silicon layer at a front surface;
• a photosensitive member extending into and at least partially surrounded by the silicon layer;
• a first doped region having a first conductivity type at a first side of the photosensitive member, wherein the first doped region is in the silicon layer;
• a second doped region having a second conductivity type different from the first conductivity type at a second side of the photosensitive member opposite to the first side, wherein the second doped region is in the silicon layer;
• a diffusion barrier structure, comprises a diffusion barrier layer and a dielectric layer at least partially surrounded by the diffusion barrier layer, wherein at least a portion of the diffusion barrier layer is between a portion of the photosensitive member and a portion of the second doped region, and the dielectric layer is in direct contact with the photosensitive member;
• and
• a superlattice layer disposed between the photosensitive member and the silicon layer.

A photo sensing device, comprising:

• a substrate, comprising a silicon layer at a front surface;
• a photosensitive member extending into and at least partially surrounded by the silicon layer;
• a first doped region having a first conductivity type at a first side of the photosensitive member, wherein the first doped region is in the silicon layer;
• and
• a second doped region having a second conductivity type different from the first conductivity type at a second side of the photosensitive member opposite to the first side, wherein the second doped region is in the silicon layer, and the second doped region comprises:
• a heavily doped region;
• and
• a lightly doped region wherein at least a portion of the lightly doped region is between the heavily doped region and the photosensitive member;
• a diffusion barrier structure extending in the lightly doped region of the second doped region;
• and
• a superlattice layer disposed between the photosensitive member and the silicon layer, wherein the diffusion barrier structure is apart from a sidewall of the superlattice layer.