Photodetector with a buried layer

1. A photodetector device comprising:

a substrate layer;

an n-type buried layer (NBL) implanted into the substrate layer;

a bottom contacting layer disposed over a surface of the substrate layer and having a first contacting region and a second contacting region, the bottom contacting layer providing a low resistance path between the first and second contacting regions, the bottom contacting layer having:

an epitaxial (EPI) layer disposed over the surface of the substrate layer and a surface of the NBL,

a first plug implanted into the EPI layer, the first plug in electrical contact with the NBL, the first plug corresponding to the first contacting region, and

a second plug implanted into the EPI layer, the second plug in electrical contact with the NBL, the second plug corresponding to the second contacting region;

an insulating layer disposed over a surface of the bottom contacting layer;

an intrinsic region disposed within the insulating layer, the intrinsic region in electrical contact with the first contacting region of the bottom contacting layer, the intrinsic region comprising a low band-gap material;

a metal contact disposed within the insulating layer and in electrical contact with the second contacting region of the bottom contacting layer;

an anode in electrical contact with the intrinsic region; and

a cathode in electrical contact with the metal contact.

2. The device of claim 1 , wherein the low band-gap material comprises Germanium (Ge), Silicon-Germanium (SiGe), or Indium Gallium Arsinide (InGaAs).

3. The device of claim 1 , wherein the insulating layer comprises an oxide.

4. The device of claim 1 , wherein the intrinsic region is formed within an etched cavity of the insulating layer, the device comprising a seed layer disposed over one or more surfaces of the etched cavity.

5. The device of claim 4 , wherein the seed layer has a crystalline structure compatible with the low band-gap material.

6. The device of claim 1 , comprising:

an encapsulating layer disposed over a surface of the insulating layer;

a first plug disposed within the encapsulating layer and providing electrical contact between the anode and the intrinsic region;

a second plug disposed within the encapsulating layer and providing electrical contact between the cathode and the meta contact.

7. The device of claim 6 , wherein the first and second plugs comprise Tungsten (W).

8. The device of claim 1 , wherein the anode entirely covers a surface of the intrinsic region.

9. The device of claim 1 , wherein the anode partially covers a surface of the intrinsic region.

10. The device of claim 1 , wherein the first and send plugs comprise a doped N-type material.

11. A method for forming a photodetector device, the method comprising:

implanting an n-type buried layer (NBL) into a substrate layer;

forming a bottom contacting layer over a surface of the substrate layer, the bottom contacting region having a first contacting region and a second contacting region, the bottom contacting layer providing a low resistance path between the first and second contacting regions, the forming of the bottom contacting layer including:

forming an epitaxial (EPI) layer over the surface of the substrate layer and a surface of the NBL;

implanting a first plug into the EPI layer, the first plug in electrical contact with the NBL, the first plug corresponding to the first contacting region; and

implanting a second plug into the EPI layer, the second plug in electrical contact with the NBL, the second plug corresponding to the second contacting region;

depositing an insulating layer over a surface of the bottom contacting layer;

etching a cavity within the insulating layer;

depositing a low band-gap material in the etched cavity of the insulating layer to form an intrinsic region, the intrinsic region in electrical contact with the first contacting region of the bottom contacting layer;

forming a metal contact in the insulating layer, the metal contact in electrical contact with the second contacting region of the bottom contacting layer;

forming an anode to be in electrical contact with the intrinsic region, wherein the anode is offset from the intrinsic region such that at least a portion of the intrinsic region is not covered by the anode; and

forming a cathode to be in electrical contact with thy: metal contact.

12. The method of claim 11 , wherein the low band-gap material comprises Germanium (Ge), Silicon-Germanium (SiGe), or Indium Gallium Arsinide (InGaAs).

13. The method of claim 11 , wherein the insulating layer comprises an oxide.

14. The method of claim 11 , comprising depositing a seed layer over one or more surfaces of the etched region of the insulating layer before depositing a low band-gap material.

15. The method of claim 14 , wherein the seed layer has a crystalline structure compatible with the low band-gap material.

16. The method of claim 11 , comprising:

forming an encapsulating layer over a surface of the insulating layer;

forming a first plug in the encapsulating layer to provide electrical contact between the anode and the intrinsic region;

forming a second plug in the encapsulating layer to provide electrical contact between the cathode and the metal contact.

17. The method of claim 16 , wherein the first and second plugs comprise Tungsten (W).

18. The device of claim 1 , wherein the anode is offset from the intrinsic region such that at least a portion of the intrinsic region is not covered by the anode.

19. The method of claim 11 , wherein the anode is offset from the intrinsic region such that at least a portion of the intrinsic region is not covered by the anode.