GERMANIUM PHOTODETECTOR WITH EXTENDED RESPONSIVITY

• US 20190035948A1
• Filed: 07/28/2017
• Published: 01/31/2019
• Est. Priority Date: 07/28/2017
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: BAYN, Igal I., ANDERSON, Sean P.
• Granted Patent: US 10,446,699 B2
• Time in Patent Office: Days
• CPC Class Codes: G01S 7/4913 Circuits for detection, sampling, integration or read-out
• CPC Class Codes: G02B 2006/12061 Silicon
• CPC Class Codes: G02B 2006/12123 Diode
• CPC Class Codes: G02B 6/42 Coupling light guides with opto-electronic elements
• CPC Class Codes: H01L 31/02027 for devices working in avalanche mode
• CPC Class Codes: H01L 31/022408 for devices characterised by at least one potential jump barrier or surface barrier
• CPC Class Codes: H01L 31/02325 the optical elements not being integrated nor being directly associated with the device
• CPC Class Codes: H01L 31/02327 the optical elements being integrated or being directly associated to the device, e.g. back reflectors optical coatings H01L31/0216
• CPC Class Codes: H01L 31/024 Arrangements for cooling, heating, ventilating or temperature compensation for photovoltaic devices H01L31/052
• CPC Class Codes: H01L 31/028 including, apart from doping material or other impurities, only elements of Group IV of the Periodic Table
• CPC Class Codes: H01L 31/035281 Shape of the body
• CPC Class Codes: H01L 31/103 the potential barrier being of the PN homojunction type

Abstract

Embodiments herein describe photonic systems that include a germanium photodetector thermally coupled to a resistive element. Current flowing through the resistive element increases the temperature of the resistive element. Heat from the resistive element increases the temperature of the thermally coupled photodetector. Increasing the temperature of the photodetector increases the responsivity of the photodetector. The bias voltage of the photodetector can be increased to increase the bandwidth of the photodetector. In various embodiments, the photodetector includes at least one waveguide to receive light into the photodetector. Other embodiments include multiple resistive elements thermally coupled to the photodetector.

Claims

1. A photonic system, comprising:

a silicon substrate that includes a waveguide;

an optical detector optically coupled to the waveguide, the optical detector comprising;

a germanium layer disposed on the silicon substrate; and

a plurality of electrical contacts contacting at least one of the silicon substrate and the germanium layer; and

a resistive element thermally coupled to the optical detector such that a current flowing through the resistive element controls a temperature of the optical detector.

2. The system of claim 1 further comprising at least one silicon bridge coupling the silicon substrate to the resistive element.

3. The system of claim 1 wherein,

the silicon substrate has a polygon shaped geometry comprising multiple sides,

the resistive element comprises at least two sides that are adjacent to at least two respective sides of the multiple sides of the silicon substrate, and further comprising a respective bridge that couples the respective adjacent sides of the resistive element and the silicon substrate.

4. The system of claim 1 wherein the resistive element is disposed on the silicon substrate.

5. The system of claim 1 wherein,

the silicon substrate has a polygon shaped geometry that includes at least four sides;

and

the resistive element includes multiple sides that are adjacent to at least one side of the silicon substrate.

6. The system of claim 1 wherein the silicon substrate includes at least one other waveguide, the at least one other waveguide comprises one of silicon and silicon nitride.

7. The system of claim 6 further comprising at least one additional resistive element thermally coupled to the optical detector such that a current flowing through the at least one additional resistive element affects the temperature of the optical detector.

8. The system of claim 6 wherein,

the silicon substrate has a polygon shape that includes a plurality of sides that form at least three corners;

the waveguide and at least one additional waveguide are arranged on the plurality of sides of the silicon substrate in a configuration that is one of symmetrical and asymmetrical;

the germanium layer is rotated such that corners of the germanium layer are aligned with the waveguides; and

some electrical contacts in the plurality of electrical contacts are symmetrically arranged at the corners of the silicon substrate,

the system further comprising at least one additional resistive element thermally coupled to the optical detector such that current flowing through the additional resistive element affects the temperature of the optical detector, wherein the resistive element and the additional resistive element are each aligned with a respective corner of the silicon substrate.

9. The system of claim 1 wherein the waveguide comprises one of silicon nitride, silicon oxy-nitride, and polysilicon.

10. The system of claim 1 wherein,

crystalline silicon substrate has a geometric shape that is one of a closed plane curve and a polygon, and

the germanium layer has a geometric shape that is one of a closed plane curve and a polygon.

11. A method comprising:

applying current to at least one resistive element that is thermally coupled to an optical detector, the optical detector comprising a germanium layer disposed on a silicon substrate, the silicon substrate comprising at least one waveguide optically coupled to the germanium layer;

adjusting the applied current to the at least one resistive element based on a comparison between an operating parameter and a threshold.

12. The method of claim 11 wherein the operating parameter is for the at least one resistive element and is at least one of a voltage, a resistance, and a temperature stored in a look-up table for the applied current.

13. The method of claim 11 wherein the operating parameter is for a different resistive element and is at least one of a voltage, a resistance, and a temperature stored in a look-up table for the applied current to the at least one resistive element.

14. The method of claim 11 wherein the operating parameter is a target resistance of the at least one resistive element and the threshold is a threshold resistance and further comprising:

monitoring a voltage drop across the at least one resistive element;

calculating a resistance of the at least one resistive element from the applied current and the voltage drop; and

comparing the calculated resistance to the target resistance.

15. The method of claim 11 further comprising monitoring a temperature of the different resistive element, wherein the operating parameter is for a different resistive element.

16. A photonic system, comprising:

a substrate that includes at least one waveguide comprising silicon;

an optical detector optically coupled to the at least one waveguide, the optical detector comprising a germanium layer disposed on the substrate; and

at least one resistive element thermally coupled to the optical detector such that a current flowing through the resistive element controls a temperature of the optical detector.

17. The system of claim 16 wherein,

the substrate has a geometric shape that is one of a closed plane curve and a polygon, and

the germanium layer has a geometric shape that is one of a closed plane curve and a polygon.

18. The system of claim 17 further comprising at least one bridge coupling the substrate to the at least one resistive element.

19. The system of claim 18 wherein,

the substrate has a polygon shape and multiple sides,

the at least one resistive element includes multiple sides that are adjacent to at least two of the multiple sides of the substrate, and

the at least one bridge is a plurality of bridges that couples the multiple sides of the at least one resistive element to the at least two of the multiple sides of the substrate.

20. The system of claim 19 wherein,

the at least one waveguide includes at least two waveguides positioned symmetrically on the substrate,

the at least one resistive element includes at least two resistive elements positioned symmetrically around the substrate,

electrical contacts are positioned symmetrically on the optical detector;

and

further comprising at least two silicon bridges coupling the substrate to the at least two resistive elements.