Doped semiconductor structure for NIR sensors

A method of forming an integrated chip structure, comprising:

• etching a base substrate comprising a first semiconductor material to form a recess defined by sidewalls and an upper surface of the base substrate;
• forming an additional doped region along the sidewalls and the upper surface of the base substrate, the additional doped region being vertically and laterally surrounded along opposing sides by the base substrate;
• performing a first deposition process to form a doped epitaxial layer along the one or more interior surfaces of the base substrate, the doped epitaxial layer and the additional doped region having a same dopant, wherein the doped epitaxial layer is laterally and vertically separated from the additional doped region by a region of the base substrate having a lower concentration of the dopant than the doped epitaxial layer and the additional doped region;
• performing a second deposition process to form an epitaxial material comprising a second semiconductor material onto the doped epitaxial layer, the epitaxial material having a maximum dopant concentration that is less than a dopant concentration of the doped epitaxial layer;
• performing a first implantation process to form a first doped photodiode region within the epitaxial material;
• and
• performing a second implantation process to form a second doped photodiode region within the epitaxial material, wherein the second doped photodiode region laterally surrounds the first doped photodiode region.

A method of forming an integrated chip structure, comprising:

• forming a recess within a silicon substrate;
• forming an in-situ doped epitaxial germanium within the recess and physically contacting the silicon substrate, the in-situ doped epitaxial germanium comprising a first concentration of a first dopant species that is between approximately 5e17 atoms/cm3 and approximately 1e20 atoms/cm3;
• forming a germanium epitaxial material to physically contact the in-situ doped epitaxial germanium and within the recess, wherein a part of the germanium epitaxial material has a gradient doping concentration of the first dopant species, the gradient doping concentration comprising a second concentration that is less than the first concentration;
• forming a first doped photodiode region within the germanium epitaxial material, the first doped photodiode region comprising a first doping type;
• forming a second doped photodiode region within the germanium epitaxial material, the second doped photodiode region comprising a second doping type;
• and
• wherein the gradient doping concentration within the germanium epitaxial material decreases from a bottommost surface of the germanium epitaxial material to a minimum dopant concentration that is non-zero distance over the bottommost surface.