Germanium metal-contact-free near-IR photodetector

Patent metadata

Field	Value
Publication number	US-10847665-B2
Application number	US-201916699363-A
Country	US
Kind code	B2
Filing date	Nov 29, 2019
Priority date	Mar 10, 2014
Publication date	Nov 24, 2020
Grant date	Nov 24, 2020

Abstract

A Ge-on-Si photodetector constructed without doping or contacting Germanium by metal is described. Despite the simplified fabrication process, the device has responsivity of 1.24 A/W, corresponding to 99.2% quantum efficiency. Dark current is 40 nA at −4 V reverse bias. 3-dB bandwidth is 30 GHz.

First claim

What is claimed is:

1. A photodetector, comprising:
a substrate;
a silicon film layer on the substrate, including an input waveguide;
a light absorber on the silicon film layer forming a hybrid waveguide with the input waveguide,
a first doped semiconductor contact in the silicon film layer underneath a first end of the light absorber;
a second doped semiconductor contact in the silicon film layer underneath a second end of the light absorber, opposite to the first end;
a first metal terminal, in electrical communication with the first contact and in electrical communication with external circuitry; and
a second metal terminal, in electrical communication with the second contact and in electrical communication with the external circuitry.

2. The photodetector according to claim 1 , wherein the first doped semiconductor contact comprises: a first slab underneath the light absorber, a second slab underneath the first metal terminal, and a first connecting slab extending in the silicon film layer between the first slab and the second slab; and
wherein the second contact comprises: a third slab underneath the light absorber, a fourth slab underneath the second metal terminal, and a second connecting slab extending in the silicon film layer between the third slab and the fourth slab.

3. The photodetector according to claim 2 , wherein the first connecting slab comprises a higher doping level than the first slab.

4. The photodetector according to claim 2 , wherein the first connecting slab comprises a doping level intermediate the respective first slab and the second slab.

5. The photodetector according to claim 2 , wherein a sheet resistance of the second slab is an order of magnitude smaller than a sheet resistance of the first connecting slab.

6. The photodetector according to claim 1 , wherein the substrate comprises a buried oxide layer under the silicon film layer.

7. The photodetector according to claim 1 , wherein the first doped semiconductor contact includes p-type doping; and wherein the second doped semiconductor contact includes n-type doping.

8. The photodetector according to claim 1 , wherein the first doped semiconductor contact includes boron doping; and wherein the second doped semiconductor contact includes phosphorus doping.

9. The photodetector according to claim 1 , wherein the light absorber consists of an intrinsic semiconductor.

10. The photodetector according to claim 1 , wherein the light absorber comprises germanium.

11. The photodetector according to claim 1 , wherein the light absorber consists of intrinsic germanium.

12. The photodetector according to claim 1 , wherein the light absorber comprises a plurality of facets providing a non-planar faceted shape.

13. The photodetector according to claim 12 , wherein the light absorber comprises a triangular cross section.

14. The photodetector according to claim 12 , wherein one of the plurality of facets is oriented at an angle between 15 degrees and 75 degrees to a surface of the substrate.

15. The photodetector according to claim 1 , wherein the light absorber includes a sidewall at a 25° angle to the silicon film layer.

16. The photodetector according to claim 1 , wherein the light absorber comprises a taper configured to adiabatically convert light from the input waveguide to the hybrid waveguide.

17. The photodetector according to claim 1 , wherein the light absorber includes a planarized surface; and further comprising a third doped semiconductor contact in electrical communication with the planarized surface.

18. The photodetector according to claim 1 , configured as an avalanche photodetector, wherein photomultiplication occurs in the light absorber.

19. The photodetector according to claim 1 , wherein the hybrid waveguide is configured to couple light into a single mode.

20. The photodetector according to claim 1 , further comprising a heater for keeping the photodetector at an elevated temperature to improve performance.

Assignees

• Elenion Tech Llc

Inventors

• Baehr-Jones Thomas
• Zhang Yi
• Hochberg Michael J
• Novack Ari

Classifications

• H10F77/122

  comprising only Group IV materials · CPC title

• H10F77/12

  Active materials · CPC title

• H10F71/1212

  consisting of germanium · CPC title

• H10F39/812

  Arrangements for transferring the charges in the image sensor perpendicular to the imaging plane, e.g. buried regions used to transfer generated charges to circuitry under the photosensitive region · CPC title

• H10F39/184

  Infrared image sensors · CPC title