Photonic device

1. A photonic device comprising:

a semiconductor layer including a first region, a second region, and a third region disposed between the first and second regions;

an insulating layer covering the semiconductor layer; and

first and second plugs extending to pass through the insulating layer and electrically connected to the corresponding first and second regions;

wherein:

the third region is configured to allow charge carriers to flow between the first and second regions;

the third region includes a portion that protrudes from a surface of the first or second region;

the first plug is in a rectifying contact with the first region; and

the second plug is in an ohmic contact with the second region.

2. The photonic device of claim 1 , further comprising:

first and second electrode pads disposed on the insulating layer;

wherein the first and second regions are electrically connected with the first and second electrode pads by the respective first and second plugs.

3. The photonic device of claim 1 , wherein:

the first and second regions have substantially similar charge carrier concentrations.

4. The photonic device of claim 3 , wherein the first and third regions are intrinsic regions.

5. The photonic device of claim 3 , wherein the first and third regions are extrinsic regions doped with dopants of a first or second conductivity type.

6. The photonic device of claim 1 , wherein:

the second region is doped with a dopant of a first or second conductivity type; and

the second region has a higher charge carrier concentration than the first region.

7. The photonic device of claim 1 , wherein:

the second region includes a first doped region of a first or second conductivity type and a second doped region of the first or second conductivity type;

the second doped region has a higher charge carrier concentration than the first doped region; and

the second plug is in an ohmic contact with the second doped region.

8. The photonic device of claim 1 , wherein at least one of the first plug and the second plug has a bottom surface contacting a top surface of the corresponding first region or second region.

9. The photonic device of claim 1 , wherein at least one of the first plug and the second plug has a bottom surface buried in the corresponding first region or second region.

10. The photonic device of claim 1 , further comprising:

a third plug extending to pass through the insulating layer and electrically connected to the first region;

wherein the third plug is in a rectifying contact with the first region.

11. The photonic device of claim 1 , wherein the first plug has a different width from the second plug.

12. The photonic device of claim 1 , wherein:

the semiconductor layer further comprises a third region that is disposed between the first and second regions, allows charges carriers to flow between the first and second regions, and provides a path along which an optical signal moves; and

the first through third regions form a phase shifter.

13. The photonic device of claim 1 , wherein the semiconductor layer further comprises a third region that protrudes from one side with respect to the first and second regions and is separated from the first and second plugs.

14. The photonic device of claim 1 , wherein:

the semiconductor layer further comprises a third region that is disposed between the first and second regions and is configured to generate charge carriers in response to an optical signal; and

the first through third regions form a photodiode.

15. The photonic device of claim 1 , wherein:

the semiconductor layer further comprises a first layer having the first region disposed at a top portion thereof and a third region configured to generate charge carriers in response to an optical signal, and a second layer disposed below the first layer and having the second region at a top portion thereof; and

the first through third regions form a photodiode.

16. The photonic device of claim 1 , wherein:

the first plug is configured to transmit a first electrical signal to the semiconductor layer; and

the second plug is configured to transmit a second electrical signal to the semiconductor layer.

17. A system, comprising:

at least one electro-optical modulator configured to modulate an optical signal to generate a modulated optical signal;

wherein each electro-optical modulator includes a phase shifter comprising:

a semiconductor layer including a first region, a second region, and a third region disposed between the first and second regions;

an insulating layer covering the semiconductor layer; and

first and second plugs extending to pass through the insulating layer and electrically connected to the corresponding first and second regions;

wherein:

the third region is configured to allow charge carriers to flow between the first and second regions;

the third region includes a portion that protrudes from a surface of the first or second region;

the first plug is in a rectifying contact with the first region and

the second plug is in an ohmic contact with the second region.

18. A method, comprising:

forming a semiconductor layer including first and second regions on a substrate;

doping the second region;

forming an insulating layer over the semiconductor layer;

forming a rectifying contact with the first region that passes through the insulating layer; and

forming an ohmic contact with the second region that passes through the insulating layer.

19. The method of claim 18 , wherein:

forming the semiconductor layer comprises forming the semiconductor layer with a third region protruding from the first and second regions;

forming a pattern over the first and third regions that exposes at least part of the second region; and

doping the second region after forming the pattern.

20. The method of claim 18 , wherein doping the second region comprises doping the second region with a carrier concentration higher than a carrier concentration of the first region.