Silicon-based modulator with optimized longitudinal doping profiles

Patent metadata

Field	Value
Publication number	US-11422394-B2
Application number	US-201916609239-A
Country	US
Kind code	B2
Filing date	Jan 25, 2019
Priority date	Jan 26, 2018
Publication date	Aug 23, 2022
Grant date	Aug 23, 2022

Abstract

A silicon modulator where the doping profile varies along the lateral and/or longitudinal position in the transition zones to achieve improved performance in terms of optical attenuation or contact access resistance or both. A modulator includes a core; a first transition zone that is a P-side region adjacent to the waveguide core, the first transition zone has a first longitudinal doping profile; and a second transition zone that is an N-side region adjacent to the core on an opposite side as the first transition region, the second transition zone has a second longitudinal doping profile; the first longitudinal doping profile has a variation of doping concentration along a longitudinal direction in the first transition region to mimic a first lateral doping profile, and the second longitudinal doping profile has a variation of doping concentration along a longitudinal direction in the second transition region to mimic a second lateral doping profile.

First claim

What is claimed is:

1. A silicon-based modulator comprising:
a waveguide core that is a PN junction region;
a first transition zone that is a P-side region adjacent to the waveguide core, the first transition zone has a first longitudinal doping profile; and
a second transition zone that is an N-side region adjacent to the waveguide core on an opposite side as the first transition region, the second transition zone has a second longitudinal doping profile;
wherein at least one of the first longitudinal doping profile and the second longitudinal doping profile has a variation of doping concentration along a longitudinal direction that extends a length parallel to the waveguide core and first and second electrical contacts.

2. The silicon-based modulator of claim 1 , wherein the variation of doping concentration is formed by a plurality of areas of different doping concentrations in the longitudinal direction.

3. The silicon-based modulator of claim 1 , wherein the variation of doping concentration results in one of lower optical losses for a given access resistance and lower access resistance for a given optical loss.

4. The silicon-based modulator of claim 1 , wherein the waveguide core has a p-type doping of p and first electrical contact has a p-type doping of p++ such that the first transition zone has k (k≥2) divisions P 1 , P 2 , . . . P k , each division effectively uniformly doped at a concentration level p 1 , p 2 , . . . p k , respectively, such that p≤p 1 <p 2 . . . <p k ≤p++, and
wherein the waveguide core has an n-type doping of n and the second electrical contact has an n-type doping of n++ such that the second transition zone has k (k≥2) divisions N 1 , N 2 , . . . N k , each division effectively uniformly doped at a concentration level n 1 , n 2 , . . . n k , respectively, such that n≤n 1 <n 2 . . . <n k ≤n++.

5. The silicon-based modulator of claim 1 , wherein the first longitudinal doping profile and the second longitudinal doping profile are different.

6. The silicon-based modulator of claim 1 , wherein one or more of the first longitudinal doping profile and the second longitudinal doping profile are periodic in the longitudinal direction.

7. The silicon-based modulator of claim 1 , wherein one or more of the first longitudinal doping profile and the second longitudinal doping profile are aperiodic in the longitudinal direction.

8. The silicon-based modulator of claim 1 , wherein one or more of the first longitudinal doping profile and the second longitudinal doping profile have a doping concentration adjacent to a corresponding electrical contact region equal therewith.

9. The silicon-based modulator of claim 1 , wherein one or more of the first longitudinal doping profile and the second longitudinal doping profile have a doping concentration adjacent to the waveguide core equal therewith.

10. The silicon-based modulator of claim 1 , wherein the variation of doping concentration mimics a lateral doping profile with constant longitudinal profile that is determined based on lower optical losses for a given access resistance or based on lower access resistance for a given optical loss.

11. A method comprising:
providing a silicon-based modulator that includes
a waveguide core that is a PN junction region;
a first transition zone that is a P-side region adjacent to the waveguide core, the first transition zone has a first longitudinal doping profile; and
a second transition zone that is an N-side region adjacent to the waveguide core on an opposite side as the first transition region, the second transition zone has a second longitudinal doping profile;
wherein at least one of the first longitudinal doping profile and the second longitudinal doping profile has a variation of doping concentration along a longitudinal direction that extends a length parallel to the waveguide core and first and second electrical contacts.

12. The method of claim 11 , wherein the variation of doping concentration is formed by a plurality of areas of different doping concentrations in the longitudinal direction.

13. The method of claim 11 , wherein the waveguide core has a p-type doping of p and the first electrical contact has a p-type doping of p++ such that the first transition zone has k (k≥2) divisions P 1 , P 2 , . . . P k , each division effectively uniformly doped at a concentration level p 1 , p 2 , . . . p k , respectively, such that p≤p 1 <p 2 . . . <p k ≤p++, and
wherein the waveguide core has an n-type doping of n and the second electrical contact has an n-type doping of n++ such that the second transition zone has k (k≥2) divisions N 1 , N 2 , . . . N k , each division effectively uniformly doped at a concentration level n 1 , n 2 , . . . n k , respectively, such that n≤n 1 <n 2 . . . <n k ≤n++.

14. The method of claim 11 , wherein the first longitudinal doping profile and the second longitudinal doping profile are different.

15. The method of claim 11 , wherein one or more of the first longitudinal doping profile and the second longitudinal doping profile are periodic in the longitudinal direction.

16. The method of claim 11 , wherein one or more of the first longitudinal doping profile and the second longitudinal doping profile are aperiodic in the longitudinal direction.

17. The method of claim 11 , wherein one or more of the first longitudinal doping profile and the second longitudinal doping profile have a doping concentration adjacent to a corresponding electrical contact region equal therewith.

18. The method of claim 11 , wherein one or more of the first longitudinal doping profile and the second longitudinal doping profile have a doping concentration adjacent to the waveguide core equal therewith.

19. A silicon-based modulator with an optimized longitudinal profile formed by a process comprising the steps of:
determining an input profile for lateral doping in a transition region in the silicon-based modulator, the transition region between a waveguide core and an electrical contact region, the input profile for the transition region is uniformly doped in an optical propagation direction that is a longitudinal direction that extends a length parallel to the waveguide core and electrical contact region;
defining a number of implantation steps and associated dopant concentrations; and
at each position along a lateral direction, determining an output profile dopant in the longitudinal direction such that its average is equal a dopant concentration of the input profile at a same lateral position.

20. The silicon-based modulator of claim 19 , wherein the input profile is determined based on lower optical losses for a given access resistance or for based on lower access resistance for a given optical loss.

Assignees

• Ciena Corp

Inventors

• Delisle-Simard Alexandre
• Painchaud Yves

Classifications

• G02F1/0156

  using free carrier absorption · CPC title

• G02F2202/105

  single crystal Si · CPC title

• G02F1/025 Primary

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

• G02F2202/06

  dopant · CPC title