Semiconductor device structure with photodetector

A semiconductor device structure, comprising:

• a photo-sensing epitaxial structure;
• a p-type doped structure and an n-type doped structure disposed over opposite sides of the photo-sensing epitaxial structure, wherein the photo-sensing structure extends across a top and a bottom of the p-type doped structure;
• and
• a buffer layer surrounding a bottom and sidewalls of the photo-sensing epitaxial structure, wherein the buffer layer is between the photo-sensing epitaxial structure and the p-type doped structure, and the buffer layer is between the photo-sensing epitaxial structure and the n-type doped structure.

A semiconductor device structure, comprising:

• a substrate;
• a first doped structure formed in the substrate;
• a second doped structure formed in the substrate;
• and
• a photo-sensing epitaxial structure at least partially surrounded by the substrate, wherein a portion of the photo-sensing epitaxial structure is between the first doped structure and the second doped structure, and the photo-sensing structure is closer to a bottom of the substrate than the first doped structure.