Optoelectronic device and method of manufacturing an optoelectronic device
An optoelectronic device comprising an optical waveguide formed in a silicon device layer of a silicon-on-insulator wafer. The optical waveguide including a semiconductor junction comprising a first doped region of semiconductor material and a second doped region of semiconductor material. The second doped region containing dopants of a different species to the first doped region. A first portion of the first doped region extends horizontally on top of the second doped region, a second portion of the first doped region extends vertically along a lateral side of the second doped region and a third portion of the first doped region protrudes as a salient from the first or second portion of the first doped region into the second doped region.
1. An optoelectronic device comprising:
a silicon-on-insulator wafer, comprising a substrate, a buried oxide (BOX) layer above the substrate, and a silicon device layer above the BOX layer;
an optical waveguide formed in the silicon device layer and including a semiconductor junction comprising:
a first doped region of semiconductor material; and
a second doped region of semiconductor material, the second doped region of semiconductor material containing dopants of a different species to the first doped region of semiconductor material, wherein:
a first portion of the first doped region of semiconductor material extends horizontally on top of the second doped region of semiconductor material and across the entire width of the waveguide, the first portion of the first doped region defining a top surface of the waveguide;
a second portion of the first doped region of semiconductor material extends vertically along a lateral side of the second doped region of semiconductor material;
a third portion of the first doped region of semiconductor material protrudes horizontally as a rounded salient from a mid-point of the second portion of the first doped region of semiconductor material into the second doped region of semiconductor material, the third portion of the first doped region having a hemi-cylindrical geometry and extending only to halfway across the width of the waveguide;
a first portion of the second doped region of semiconductor material immediately below the third portion of the first doped region extends vertically and continuously from the third portion of the first doped region to the BOX layer, the entire first portion of the second doped region being vertically between the third portion of the first doped region and the BOX layer, and no portion of the first doped region being vertically between the third portion of the first doped region and the BOX layer;
a second portion of the second doped region of semiconductor material immediately above the third portion of the first doped region extends vertically and continuously from the third portion of the first doped region to the first portion of the first doped region, the entire second portion of the second doped region being vertically between the third portion of the first doped region and the first portion of the first doped region; and
a third portion of the second doped region of semiconductor material comprises the entire portion of the second doped region that is immediately below the first portion of the first doped region and that is not overlapping with the third portion of the first doped region, the first portion of the second doped region, and the second portion of the second doped region, the third portion of the second doped region extending vertically and continuously from the first portion of the first doped region to the BOX layer.
2. The optoelectronic device according to claim 1 , further comprising a first heavily doped region, and a second heavily doped region, wherein the first heavily doped region and second heavily doped region are formed outside of a light propagation region of the optical waveguide, and wherein the first heavily doped region contains dopants of the same species as the first doped region of semiconductor material, and the second heavily doped region contains dopants of the same species as the second doped region of semiconductor material.
3. The optoelectronic device according to claim 2 , wherein an extension of the first doped region of semiconductor material extends from the light propagation region of the optical waveguide to the first heavily doped region, and an extension of the second doped region of semiconductor material extends from the light propagation region of the optical waveguide to the second heavily doped region.
4. The optoelectronic device according to claim 2 , wherein the optoelectronic device further comprises a first electrical contact electrically connected to the first heavily doped region, and a second electrical contact electrically connected to the second heavily doped region.
5. A method of manufacturing the optoelectronic device of claim 1 ,
wherein the method comprises the steps of:
creating the first portion of the first doped region of semiconductor material;
creating the second portion of the first doped region of semiconductor material; and
creating the third portion of the first doped region of semiconductor material.
6. The method according to claim 5 , wherein the step of creating the third portion of the first doped region of semiconductor material comprises:
depositing a first mask layer on the silicon device layer;
creating an opening in the first mask layer to the silicon device layer; and
introducing a first dopant to the silicon device layer through the opening in the first mask layer.
7. The method according to claim 6 , wherein, to create the third portion of the first doped region of semiconductor material, the first dopant is introduced to the optical waveguide through the opening in the first mask layer by diffusion of the first dopant.
8. The method according to claim 6 , wherein the first dopant is boron.
9. The method according to claim 6 , wherein the steps of creating the first portion of the first doped region of semiconductor material and the second portion of the first doped region of semiconductor material comprises:
depositing a second mask layer on the optical waveguide; and
introducing the first dopant to the optical waveguide through the second mask layer.
10. The method according to claim 9 , wherein, to create the first portion of the first doped region of semiconductor material and the second portion of the first doped region of semiconductor material, the first dopant is introduced to the optical waveguide through the second mask layer by implantation of the first dopant at less than 90° relative to the horizontal.
11. The method according to claim 6 , wherein the method further comprises:
creating a first heavily doped region outside of a light propagation region of the optical waveguide, the first heavily doped region containing dopants of the same species as the first doped region of semiconductor material; and
creating a second heavily doped region outside of the light propagation region of the optical waveguide, the second heavily doped region containing dopants of the same species as the second doped region of semiconductor material.
12. The method according to claim 11 , wherein the step of creating the first heavily doped region comprises introducing the first dopant to a region of the silicon device layer of the silicon-on-insulator wafer outside of the light propagation region of the optical waveguide.
13. The method according to claim 12 , wherein, in the step of creating the first heavily doped region, the first dopant is introduced by implantation of the first dopant.
14. The method according to claim 11 , wherein the step of creating the second heavily doped region comprises introducing a second dopant to a region of the silicon device layer of the silicon-on-insulator wafer outside of the light propagation region of the optical waveguide, the second dopant having an opposite doping type to the first dopant.
15. The method according to claim 11 , further comprising:
depositing a passivation layer on the optical waveguide;
applying a first electrical contact through the passivation layer to the first heavily doped region; and
applying a second electrical contact through the passivation layer to the second heavily doped region.
16. The method according claim 5 , wherein the method further comprises:
depositing a waveguide mask layer on the silicon device layer of the silicon-on-insulator wafer; and
etching a portion of the silicon device layer of the silicon-on-insulator wafer to form the optical waveguide.
17. The method according to claim 5 , wherein the silicon device layer of the silicon-on-insulator wafer contains dopants of a different species to the first doped region of semiconductor material, and the silicon device layer of the silicon-on-insulator wafer provides the second doped region of semiconductor material.
18. A Mach-Zehnder interferometer, usable as an electro-optic modulator, the interferometer including a pair of waveguides, each waveguide containing the optoelectronic device of claim 1 .