Germanium-containing photodetector and methods of forming the same

1. A method of forming a photodetector, comprising:

forming a trench in a single crystalline silicon substrate;

performing an epitaxial deposition process that grows a germanium-containing well within the trench, wherein the germanium-containing well comprises a germanium-containing material that is in epitaxial alignment with the single crystalline silicon substrate;

vertically recessing an upper portion of the germanium-containing well in an upper portion of the trench;

forming a silicon-containing capping structure on a top surface of the germanium-containing well; and

forming at least one photovoltaic junction within, or across, the trench by implanting dopants of a first conductivity type and dopants of a second conductivity type.

2. The method of claim 1 , wherein:

dopants of the first conductivity type are implanted into a first portion of the germanium-containing well to form a first-conductivity-type germanium-containing region; and

dopants of the second conductivity type are implanted into a second portion of the germanium-containing well to form a second-conductivity-type germanium-containing region.

3. The method of claim 2 , wherein the at least one photovoltaic junction comprises a p-i-n junction or a p-n junction formed within the germanium-containing well.

4. The method of claim 1 , wherein:

dopants of the first conductivity type are implanted through a sidewall and a bottom surface of the trench to form a first-conductivity-type silicon region within the single crystalline silicon substrate; and

dopants of the second conductivity type are implanted into a portion of the germanium-containing well to form a second-conductivity-type germanium-containing region.

5. The method of claim 4 , wherein the at least one photovoltaic junction comprises a p-i-n junction or a p-n junction formed across the germanium-containing well and the single crystalline silicon substrate.

6. The method of claim 1 , further comprising:

forming a sensing circuit on the single crystalline silicon substrate or on a semiconductor substrate that is different from the single crystalline silicon substrate; and

electrically connecting a second-conductivity-type germanium-containing region and the sensing circuit by forming metal interconnect structures on the second-conductivity-type germanium-containing region and the sensing circuit.

7. The method of claim 1 , further comprising:

forming a first-conductivity-type silicon region contacting the first-conductivity-type germanium-containing region in a first region of the silicon-containing capping structure; and

forming a second-conductivity-type silicon region contacting the second conductivity type germanium-containing region in a second region of the silicon-containing capping structure.

8. The method of claim 7 , wherein a passivation silicon region having an atomic concentration of dopants in a range from 1.0×10 13 /cm 3 to 1.0×10 17 /cm 3 is located between the first-conductivity-type silicon region and the second-conductivity-type silicon region after formation of the first-conductivity-type silicon region and the second-conductivity-type silicon region.

9. The method of claim 1 , further comprising forming a single crystalline silicon liner on sidewalls and a bottom surface of the trench, wherein:

the single crystalline silicon liner is epitaxially aligned to the single crystalline silicon substrate; and

the germanium-containing well is formed on an inner sidewall of the single crystalline silicon liner.

10. The method of claim 1 , wherein the at least one photovoltaic junction comprises two or more p-n junctions containing two or more p-doped germanium-containing regions and two or more n-doped germanium-containing regions.

11. A method of forming a semiconductor structure, the method comprising:

forming a trench in an upper portion of a single crystalline silicon substrate;

forming a first-conductivity-type silicon region around the trench within the single crystalline silicon substrate;

forming a germanium-containing well in the trench;

forming a silicon-containing capping structure on a top surface of the germanium-containing well;

forming a second-conductivity-type germanium-containing region by doping an upper portion of the germanium-containing well with dopants of a second conductivity type; and

forming field effect transistors in a photodetector region and in a sensing circuit region on the single crystalline silicon substrate.

12. The method of claim 11 , further comprising:

epitaxially depositing a germanium-containing material in the trench, wherein the germanium-containing material is epitaxially aligned to the single crystalline silicon substrate; and

vertically recessing the germanium-containing material, wherein a remaining portion of the germanium-containing material comprises the germanium-containing well.

13. The method of claim 11 , further comprising growing a silicon liner comprising single crystalline silicon from sidewalls and a bottom surface of the trench, wherein the germanium-containing well is formed inside the silicon liner.

14. The method of claim 11 , further comprising forming dielectric material layers and metal interconnect structures over the field effect transistors, wherein the metal interconnect structures comprise metal via structures that are electrically connected to a respective one of the first-conductivity-type silicon region and the second-conductivity-type germanium-containing region.

15. A method of forming a photodetector, comprising:

depositing and patterning a dielectric mask layer over a single crystalline silicon substrate;

etching a trench in the single crystalline silicon substrate through an opening in the dielectric mask layer;

performing an epitaxial deposition process that grows a germanium-containing material, whereby a germanium-containing well is formed within the trench;

forming a silicon-containing capping structure on a top surface of the germanium-containing well; and

forming a photovoltaic junction within, or across, the trench by implanting dopants of a first conductivity type and dopants of a second conductivity type.

16. The method of claim 15 , wherein a portion of the germanium-containing material that grows within the trench is formed with epitaxial alignment with the single crystalline silicon substrate within the trench.

17. The method of claim 16 , further comprising:

removing excess portions of the germanium-containing material from above a horizontal plane including a top surface of the dielectric mask layer; and

the method comprises vertically recessing a remaining portion of the germanium-containing material within the opening in the dielectric mask layer.

18. The method of claim 15 , further comprising:

forming a first-conductivity-type germanium-containing region by implanting dopants of the first conductivity type into a first portion of the germanium-containing well; and

forming a second-conductivity-type germanium-containing region by implanting dopants of the second conductivity type into a second portion of the germanium-containing well.

19. The method of claim 18 , wherein the photovoltaic junction comprises a p-i-n junction or a p-n junction formed within the germanium-containing well.

20. The method of claim 15 , further comprising:

forming a first-conductivity-type silicon region by implanting dopants of the first conductivity type through a sidewall and a bottom surface of the trench into the single crystalline silicon substrate; and

forming a second-conductivity-type germanium-containing region by implanting dopants of the second conductivity type into a portion of the germanium-containing well,

wherein the photovoltaic junction comprises a p-i-n junction or a p-n junction that is formed across the germanium-containing well and the single crystalline silicon substrate.