WE CLAIM:
1. A semiconductor device comprising:
a monocrystalline silicon region including a taper structure (120) to receive light;
a first buried oxide region (130) adjacent to the taper structure at a first side of the first buried oxide region, the first buried oxide region to redirect the light toward a first end of the taper structure;
a polycrystalline silicon region (132) adjacent to the first buried oxide region at a second side of the first buried oxide region opposite the first side; and
a photodetector (160) adjacent to the monocrystalline silicon region, the photodetector coupled to receive the light via the first end and to generate an electrical signal based on the light, wherein a trench structure (126) is formed at least in part by a recess of the first buried oxide toward the polycrystalline silicon region, wherein a bottom side of the photodetector adjoins silicon disposed in the trench structure.
2. The semiconductor device of claim 1, wherein the photodetector extends to a top of the trench structure.
3. The semiconductor device of claim 1, the semiconductor device further comprising one or more mirror structures to receive a portion of the light from the photodetector, the one or more mirror structures to reflect the portion of the light back toward the photodetector.

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4. The semiconductor device of claim 1, the monocrystalline silicon region having formed therein a first waveguide trench (170,172) and a second waveguide trench (174,176), wherein the light is directed toward the photodetector between the first waveguide trench and the second waveguide trench.
5. The semiconductor device of claim 4, wherein a first distance between the first waveguide trench and the second waveguide trench at the photodiode is less than a second distance between the first waveguide trench and the second waveguide trench at the taper structure.
6. The semiconductor device of claim 1, wherein the photodetector comprises a Germanium photodiode.
7. The semiconductor device of claim 6, wherein the Germanium photodiode comprises:
a first lobe portion (162) including p-doped Germanium; a second lobe portion (166) including n-doped Germanium; and a neck portion (164) between the first lobe portion and a second lobe portion, the neck portion including intrinsic Germanium.
8. A method of fabricating a semiconductor device, the method
comprising:
forming a monocrystalline silicon region, including:
growing a monocrystalline silicon epitaxy (210) on a wafer (102) including a buried barrier layer (104); and

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etching the monocrystalline silicon epitaxy (220) to form a taper structure (122) of the monocrystalline silicon region;
disposing an oxide material (230) on the monocrystalline silicon region to form a first oxide region (130) adjacent to the taper structure;
forming (240) a polycrystalline silicon region (132) on the first oxide region;
after forming the polycrystalline silicon region, removing a portion (250) from the wafer to expose the monocrystalline silicon region, the portion including the buried barrier layer; and
forming a photodetector (260) adjacent to the monocrystalline silicon region, wherein a trench structure (126) is formed at least in part by a recess of the first oxide region toward the polycrystalline silicon region, wherein a bottom side of the photodetector adjoins silicon disposed in the trench structure.
9. The method of claim 8 , wherein the photodetector extends to a top of the trench structure.
10. The method of claim 8 , wherein forming the monocrystalline silicon region further comprises etching one or more recesses in the wafer, and wherein disposing the oxide material on the monocrystalline silicon region further forms one or more mirror structures each in a respective one of the one or more recesses.
11. The method of claim 8, further comprising etching the monocrystalline silicon region to form a first waveguide trench and a second waveguide trench.

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12. The method of claim 11 , wherein a first distance between the first waveguide trench and the second waveguide trench at the photodiode is less than a second distance between the first waveguide trench and the second waveguide trench at the taper structure.
13. The method of claim 8, wherein removing the portion of the wafer comprises splitting the wafer at the buried barrier layer.
14. A system comprising:
a semiconductor device including:
a monocrystalline silicon region including a taper structure (120) to receive light;
a first buried oxide region (130) adjacent to the taper structure at a first side of the first buried oxide region, the first buried oxide region to redirect the light toward a first end of the taper structure;
a polycrystalline silicon region (132) adjacent to the first buried oxide region at a second side of the first buried oxide region opposite the first side; and
a photodetector (160) adjacent to the monocrystalline silicon region, the photodetector coupled to receive the light via the first end and to generate an electrical signal based on the light, wherein a trench structure is formed at least in part by a recess of the first buried oxide toward the polycrystalline silicone region, wherein a bottom side of the photodetector adloins silicone disposed in the trench structure; and
a first device coupled to an input of the semiconductor device, the first device to generate the light; and

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a second device electrically coupled to the photodetector, the second device to receive and process the electrical signal.
15. The system of claim 14, wherein the photodetector extends to a top of the trench structure.
16. The system of claim 14, the semiconductor device further comprising one or more mirror structures to receive a portion of the light from the photodetector, the one or more mirror structures to reflect the portion of the light back toward the photodetector.
17. The system of claim 14, the monocrystalline silicon region having formed therein a first waveguide trench and a second waveguide trench, wherein the light is directed toward the photodetector between the first waveguide trench and the second waveguide trench.
18. The system of claim 17, wherein a first distance between the first waveguide trench and the second waveguide trench at the photodiode is less than a second distance between the first waveguide trench and the second waveguide trench at the taper structure.
19. The system of claim 14, wherein the photodetector comprises a Germanium photodiode.

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20. The system of claim 19, wherein the Germanium photodiode comprises:
a first lobe portion (162) including p-doped Germanium;
a second lobe portion (166) including n-doped Germanium; and
a neck portion (164) between the first lobe portion and a second lobe portion, the neck portion including intrinsic Germanium.
Dated this 28th day of June 2019
(P. Dileep Kumar) Registration Number: IN/PA-1364 For Law Firm of Naren Thappeta Agent for Applicant

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