Photodetectors including a coupling region with multiple tapers
Structures for a photodetector and methods of fabricating a structure for a photodetector. A photodetector includes a photodetector pad coupled to a waveguide core and a light-absorbing layer coupled to the photodetector pad. The light-absorbing layer has a body, a first taper that projects laterally from the body toward the waveguide core, and a second taper that projects laterally from the body toward the waveguide core. The photodetector pad includes a tapered section that is laterally positioned between the first taper and the second taper of the light-absorbing layer.
1. A structure comprising:
a waveguide core; and
a photodetector including a photodetector pad coupled to the waveguide core and a light-absorbing layer coupled to the photodetector pad, the light-absorbing layer including a body, a first taper that projects laterally from the body toward the waveguide core, and a second taper that projects laterally from the body toward the waveguide core, the photodetector pad having a side surface, the first taper and the second taper of the light-absorbing layer each having a respective non-pointed tip that is spaced from the side surface by a gap, and the photodetector pad including a tapered section that is laterally positioned between the first taper and the second taper of the light-absorbing layer,
wherein the waveguide core is connected to the side surface of the photodetector pad, and the waveguide core is tapered with a width that increases with decreasing distance from the side surface of the photodetector pad.
2. The structure of claim 1 wherein the tapered section of the photodetector pad and the waveguide core are aligned along a longitudinal axis.
3. The structure of claim 1 wherein the photodetector pad and the waveguide core comprise single-crystal silicon, and the light-absorbing layer comprises germanium.
4. The structure of claim 1 wherein the photodetector pad includes an anode and a cathode, and the light-absorbing layer is laterally positioned between the anode and the cathode.
5. The structure of claim 1 wherein the photodetector pad has a top surface, and the light-absorbing layer is positioned on the top surface of the photodetector pad.
6. The structure of claim 1 wherein the photodetector pad has a top surface and a trench extending from the top surface partially through the photodetector pad, and the light-absorbing layer is positioned in the trench.
7. The structure of claim 1 wherein the tapered section of the photodetector pad has a width that decreases with increasing distance from the side surface of the photodetector pad.
8. The structure of claim 1 wherein the first taper has a first side surface, the second taper has a second side surface, and the first side surface of the first taper is laterally separated from the second side surface of the second taper by a distance that increases with decreasing distance from the side surface of the photodetector pad.
9. The structure of claim 8 wherein the tapered section of the photodetector pad has a width that decreases with increasing distance from the side surface of the photodetector pad.
10. The structure of claim 1 wherein the photodetector pad is wider than the body of the light-absorbing layer.
11. The structure of claim 1 wherein the first taper diverges away from the second taper with increasing distance from the body.
12. A structure comprising:
a waveguide core; and
a photodetector including a photodetector pad coupled to the waveguide core and a light-absorbing layer coupled to the photodetector pad, the light-absorbing layer including a body, a first taper that projects laterally from the body toward the waveguide core, and a second taper that projects laterally from the body toward the waveguide core, and the photodetector pad including a tapered section that is laterally positioned between the first taper and the second taper of the light-absorbing layer,
wherein the photodetector pad has a side surface, the waveguide core is coupled to a portion of the side surface, the first taper has a first side surface, the second taper has a second side surface, and the first side surface of the first taper is laterally separated from the second side surface of the second taper by a distance that is constant with decreasing distance from the side surface of the photodetector pad.
13. The structure of claim 12 wherein the tapered section of the photodetector pad has a width that decreases with increasing distance from the side surface.
14. The structure of claim 12 wherein the photodetector pad and the waveguide core comprise single-crystal silicon, and the light-absorbing layer comprises germanium.
15. The structure of claim 12 wherein the photodetector pad includes an anode and a cathode, and the light-absorbing layer is laterally positioned between the anode and the cathode.
16. A structure comprising:
a waveguide core; and
a photodetector including a photodetector pad coupled to the waveguide core and a light-absorbing layer coupled to the photodetector pad, the light-absorbing layer including a body, a first taper that projects laterally from the body toward the waveguide core, and a second taper that projects laterally from the body toward the waveguide core, and the photodetector pad including a tapered section that is laterally positioned between the first taper and the second taper of the light-absorbing layer,
wherein the photodetector pad has a side surface, the waveguide core is coupled to a portion of the side surface, the first taper has a first side surface, the second taper has a second side surface, and the first side surface of the first taper is laterally separated from the second side surface of the second taper by a distance that decreases with decreasing distance from the side surface of the photodetector pad.
17. The structure of claim 16 wherein the tapered section of the photodetector pad has a width that decreases with increasing distance from the side surface.
18. The structure of claim 16 wherein the photodetector pad and the waveguide core comprise single-crystal silicon, and the light-absorbing layer comprises germanium.
19. The structure of claim 16 wherein the photodetector pad includes an anode and a cathode, and the light-absorbing layer is laterally positioned between the anode and the cathode.