Method for manufacturing a germanium slow light waveguide and photodiode incorporating this slow light waveguide

Patent metadata

Field	Value
Publication number	US-10132998-B2
Application number	US-201715660183-A
Country	US
Kind code	B2
Filing date	Jul 26, 2017
Priority date	Jul 28, 2016
Publication date	Nov 20, 2018
Grant date	Nov 20, 2018

Abstract

This method for manufacturing a germanium slow light waveguide includes:
producing, in a silicon plate, a cavity the cross section of which, parallel to the plane of the plate, is identical to the horizontal cross section of the slow light waveguide and the bottom of which is located inside the silicon plate; then carrying out an operation of vapor phase epitaxial growth of germanium on the bottom of the cavity until this cavity is completely filled with germanium; and before implementing said epitaxial growth operation, a protective layer is deposited on an upper face of the silicon plate or, after implementing said epitaxial growth operation, the germanium that has grown on said upper face is removed.

First claim

The invention claimed is:

1. A photodiode including:
a silicon plate extending mainly in a plane referred to as the “plane of the plate”;
a first waveguide including a strip that is capable of guiding an optical signal from an input, intended to receive an optical signal to be detected, to an output, this strip being formed on the plate;
a germanium slow light waveguide extending along an optical axis from a first input that is optically coupled to the output of the first waveguide, this slow light waveguide including:
two doped regions with opposite signs, positioned on either side of the optical axis so as to capture the charge carriers generated by the optical signal propagating through this slow light waveguide; and
a horizontal cross section, parallel to the plane of the plate, that exhibits patterns positioned symmetrically on either side of the optical axis and repeated at regular intervals p along this optical axis so as to slow the propagation of the optical signal through the slow light waveguide, this pattern including two lateral teeth each positioned on a respective side of a germanium central strip or a silicon cylindrical pad that passes from one side of the germanium central strip to the other,

wherein:
the photodiode includes a cavity hollowed out of the silicon plate, the bottom of which is located inside the silicon plate and the cross section of which, parallel to the plane of the plate, is identical to the horizontal cross section of the slow light waveguide; and
the slow light waveguide completely fills this cavity and extends, in a direction perpendicular to the plane of the plate, from the bottom of this cavity up to an upper face located at the same level as or above the upper face of the plate.

2. Photodiode according to claim 1 , in which the photodiode also includes:
a second waveguide including a strip that is capable of guiding an optical signal from another input, intended to receive another optical signal to be detected, to another output, this strip being formed on the plate; and
the slow light waveguide includes, along the optical axis and on the opposite side to the first input, a second input that is optically coupled to the output of the second waveguide.

3. Photodiode according to claim 1 , in which:
the slow light waveguide includes a central strip that extends along the optical axis in order to guide the optical signal along this optical axis; and
the pattern includes the two lateral teeth each positioned on a respective side of the central strip and symmetrical to one another with respect to a longitudinal plane, this longitudinal plane being perpendicular to the plane of the plate and containing the optical axis, the length of each of these teeth being greater than or equal to the width of the central strip, the length of a tooth being equal to the shortest distance between its distal end and the longitudinal plane and the width of the central strip being equal to the shortest distance between two vertical flanks facing this central strip, each located on a respective side of the optical axis and between two successive teeth.

4. Photodiode according to claim 3 , in which the length of more than a third of the teeth is twice greater than or equal to the width of the central strip.

5. Photodiode according to claim 1 , in which the plate includes doped regions of opposite signs in direct contact with the slow light waveguide, these doped regions of the plate including doped vertical edges of the cavity in direct mechanical and electrical contact with vertical flanks of the slow light waveguide.

6. Photodiode according to claim 1 , in which the output of the first waveguide is facing and in direct mechanical contact with the first input of the slow light waveguide.

7. Photodiode according to claim 1 , in which the thickness of the slow light waveguide is equal to the depth of the cavity.

8. Photodiode according to claim 1 , in which the silicon plate extends directly over a dielectric layer, itself directly deposited on a substrate.

Assignees

• Commissariat Energie Atomique

Inventors

• Hassan Karim
• Fowler Daivid
• Kopp Christophe
• Szelag Bertrand

Classifications

• H01L31/02327

  Electricity · mapped topic

• G02B2006/12123

  Diode · CPC title

• H01L31/105

  Electricity · mapped topic

• G02B6/131 Primary

  by using epitaxial growth (epitaxial growth for semiconductors H10P14/20) · CPC title

• G02B6/122

  Basic optical elements, e.g. light-guiding paths · CPC title