Vertical PN silicon modulator

Patent metadata

Field	Value
Publication number	US-9523870-B2
Application number	US-201514680823-A
Country	US
Kind code	B2
Filing date	Apr 7, 2015
Priority date	Apr 7, 2015
Publication date	Dec 20, 2016
Grant date	Dec 20, 2016

Abstract

A silicon waveguide comprising a waveguide core that comprises a first positively doped (P1) region vertically adjacent to a second positively doped (P2) region. The P2 region is more heavily positively doped than the P1 region. A first negatively doped (N1) region is vertically adjacent to a second negatively doped (N2) region. The N2 region is more heavily negatively doped than the N1 region. The N2 region and the P2 region are positioned vertically adjacent to form a positive-negative (PN) junction. The N1 region, the N2 region, the P1 region, and the P2 region are positioned as a vertical PN junction and configured to completely deplete the P2 region of positive ions and completely deplete the N2 region of negative ions when a voltage drop is applied across the N1 region, the N2 region, the P1 region, and the P2 region.

First claim

What is claimed is:

1. An optical modulator comprising:
a silicon waveguide comprising a waveguide core that comprises:
a first positively doped (P1) region vertically adjacent to a second positively doped (P2) region such that the P2 region is more heavily positively doped than the P1 region; and
a first negatively doped (N1) region vertically adjacent to a second negatively doped (N2) region such that the N2 region is more heavily negatively doped than the N1 region, wherein the N2 region and the P2 region are positioned vertically adjacent to form a positive-negative (PN) junction;

at least one cathode; and
at least one anode selectively electrically coupled to the cathode across the waveguide core via the PN junction such that a voltage drop applied between the cathode and the anode modulates an optical carrier passing through the PN junction by changing a refractive index of the waveguide core,
wherein the P2 region is smaller than the P1 region and the N2 region is smaller than the N1 region such that the P2 and N2 regions have a greater effect on the refractive index change than the P1 and N1 regions, and such that the P1 and N1 regions have a lesser effect on optical loss of the optical carrier than the P2 and N2 regions, and
wherein the P1 region extends laterally without progressing to the anode and the N1 region extends laterally without processing to the cathode.

2. The optical modulator of claim 1 , wherein the P2 region comprises a thickness selected such that the P2 region is completely depleted of positive ions when the voltage drop is applied between the cathode and the anode.

3. The optical modulator of claim 2 , wherein the N2 region comprises a thickness selected such that the N2 region is completely depleted of negative ions when the voltage drop is applied between the cathode and the anode.

4. The optical modulator of claim 1 , wherein the P2 region is formed by in-situ doped growth.

5. The optical modulator of claim 1 , wherein the N2 region is formed by in-situ doped growth.

6. The optical modulator of claim 1 , wherein the P2 region is formed by surface doping.

7. The optical modulator of claim 1 , wherein the N2 region is formed by surface doping.

8. The optical modulator of claim 1 , wherein the waveguide further comprises:
a third positively doped (P+) region horizontally adjacent to the P1 region such that the P+ region is more heavily positively doped than the P1 region; and
a third negatively doped (N+) region horizontally adjacent to the N1 region such that the N+ region is more heavily negatively doped than the N1 region,
wherein the P+ region and the N+ region are positioned outside of the waveguide core such that the P+ region and N+ region have a minimized effect on the optical loss of the optical carrier with respect to the N1 region, the N2 region, the P1 region, and the P2 region and such that the P+ region and the N+ region reduce electrical resistance between the cathode and the anode with respect to the N1 region, the N2 region, the P1 region, and the P2 region.

9. The optical modulator of claim 8 , wherein the waveguide further comprises a fourth positively doped (P3) region positioned between the P1 region and the P+ region and positioned between the N1 region and the P+ region such that the P3 region and the N1 region create a horizontal PN junction.

10. The optical modulator of claim 1 , wherein the waveguide further comprises:
a plurality of positively doped (P++) poles vertically adjacent to the P1 region such that the P++ poles are more heavily positively doped than the P1 region, wherein the P++ poles are separated by a dielectric portion of the waveguide; and
a plurality of negatively doped (N++) regions horizontally adjacent to the N1 region such that the N++ regions are more heavily negatively doped than the N1 region and such that the N++ regions are separated by the N1 region,
wherein the P++ poles and the N++ regions are positioned outside of the waveguide core such that the P++ poles and the N++ regions have a minimized effect on the optical loss of the optical carrier with respect to the N1 region, the N2 region, the P1 region, and the P2 region and such that the P++ poles and the N++ regions reduce electrical resistance between the cathode and the anode with respect to the N1 region, the N2 region, the P1 region, and the P2 region,
wherein the anode is vertically adjacent and directly coupled to the P++ poles, and
wherein the at least one cathode comprises a cathode directly coupled to each N++ region.

11. The optical modulator of claim 10 , wherein the waveguide further comprises a plurality of positively doped (P+) regions, each P+ region positioned between one of the P++ poles and the P1 region such that the P+ regions are less heavily positively doped than the P++ poles and more heavily positively doped than the P1 region.

12. The optical modulator of claim 10 , wherein the waveguide further comprises a plurality of negatively doped (N+) regions, each N+ region positioned between one of the N++ regions and the N1 region such that the N+ regions are less heavily positively doped than the N++ regions and more heavily positively doped than the N1 region.

13. The optical modulator of claim 1 , wherein the waveguide further comprises:
a plurality of positively doped (P++) poles horizontally adjacent to the P1 region such that the P++ poles are more heavily positively doped than the P1 region, wherein the P++ poles are separated by the P1 region; and
a plurality of negatively doped (N++) regions horizontally adjacent to the N1 region such that the N++ regions are more heavily negatively doped than the N1 region and such that the N++ regions are separated by the N1 region,
wherein the at least one anode comprises an anode coupled to each P++ pole,
wherein the at least one cathode comprises a cathode coupled to each N++ region, and
wherein the P++ poles and the N++ regions are positioned outside of the waveguide core such that the P++ poles and the N++ regions have a minimized effect on the optical loss of the optical carrier with respect to the N1 region, the N2 region, the P1 region, and the P2 region and such that the P++ poles and the N++ regions reduce electrical resistance between the cathodes and the anodes with respect to the N1 region, the N2 region, the P1 region, and the P2 region.

14. The optical modulator of claim 13 , wherein the waveguide further comprises a plurality of positively doped (P+) regions, each P+ region positioned between one of the P++ poles and the P1 region such that the P+ regions are less heavily positively doped than the P++ poles and more heavily positively doped than the P1 region.

15. The optical modulator of claim 13 , wherein the waveguide further comprises a plurality of negatively doped (N+) poles, each N+ pole positioned between one of the N++ regions and the N1 region such that the N+ poles are less heavily positively doped than the N++ regions and more heavily positively doped than the N1 region.

16. An optical modulator prepared by a process comprising:
doping a first negatively doped (N1) region of a silicon wafer to create a vertically adjacent second negatively doped (N2) region such that the N2 region is more heavily negatively doped than the N1 region; and
doping a first positively doped (P1) region and a vertically adjacent second positively doped (P2) region vertically adjacent to the N2 region such that the P2 region is more heavily positively doped than the P1 region and such that the P2 region and the N2 region form a depletion region of a vertical positive-negative (PN)

Assignees

• Futurewei Technologies Inc

Inventors

• Wei Hongzhen
• Yang Li
• Xu Qianfan
• Shen Xiao

Classifications

• H10P50/642

  Chemical etching · CPC title

• H10P32/1406

  by ion implantation · CPC title

• H10P32/171

  being group IV material · CPC title

• H10P32/30

  Diffusion for doping of conductive or resistive layers · CPC title

• G02F1/025 Primary

  in an optical waveguide structure (G02F1/017, {G02F1/2257} take precedence) · CPC title