Plasmon-enhanced terahertz graphene-based photodetector and method of fabrication

Patent metadata

Field	Value
Publication number	US-10084102-B2
Application number	US-201615555132-A
Country	US
Kind code	B2
Filing date	Mar 1, 2016
Priority date	Mar 2, 2015
Publication date	Sep 25, 2018
Grant date	Sep 25, 2018

Abstract

A plasmon-enhanced terahertz graphene-based photodetector exhibits an increased absorption efficiency attained by utilizing a tunable plasmonic resonance in sub-wavelengths graphene micro-ribbons formed on SiC substrate in contact with an array of bi-metallic electrode lines. The orientation of the graphene micro-ribbons is tailored with respect to the array of sub-wavelengths bi-metallic electrode lines. The graphene micro-ribbons extend at the angle of approximately 45 degrees with respect to the electrode lines in the bi-metal electrodes array. The plasmonic mode is efficiently excited by an incident wave polarized perpendicular to the electrode lines, and/or to the graphene micro-ribbons. The absorption of radiation by graphene is enhanced through tunable geometric parameters (such as, for example, the width of the graphene micro-ribbons) and control of a carrier density in graphene achieved through tuning the gate voltage applied to the photodetector.

First claim

What is claimed is:

1. A plasmon-enhanced terahertz graphene-based photodetector, comprising:
a substrate,
a micro-ribbon array formed on said substrate, said micro-ribbon array including a plurality of graphene micro-ribbons of a predetermined width extending in a spaced apart relationship one with respect to another, and
an array of electrode lines formed in electrical contact with said micro-ribbon array, said electrode lines extending in spaced apart relationship one with respect to another,
wherein said micro-ribbons are sandwiched between said array of electrode lines and said substrate and extend in an angled relationship different than 90 degrees to said electrode lines.

2. The plasmon-enhanced terahertz graphene-based photodetector of claim 1 , further including an electrolyte layer positioned atop and enveloping said micro-ribbon array and said array of electrode lines.

3. The plasmon-enhanced terahertz graphene-based photodetector of claim 2 , further including a source terminal and a drain terminal coupled to two outermost electrical lines of said array of electrode lines,
a gate terminal coupled to said electrolyte layer, and
a source of gate voltage applied between said source and gate terminals.

4. The plasmon-enhanced terahertz graphene-based photodetector of claim 3 , further including a source of a polarized light, wherein said polarized light is incident on said micro-ribbon array and said array of electrode lines and is polarized substantially in perpendicular to micro-sized elements selected from a group consisting of: said graphene micro-ribbons, said electrode lines, and combination thereof.

5. The plasmon-enhanced terahertz graphene-based photodetector of claim 4 , wherein said electrode lines extend substantially in parallel one with respect to another with the spacing therebetween not exceeding the free space wavelength of said incident light, wherein the width of each of said electrode lines ranges from 1 μm to 2 μm, and said spacing therebetween ranges from 0.6 μm to 7.3 μm.

6. The plasmon-enhanced terahertz graphene-based photodetector of claim 3 , wherein upon application of said gate voltage of a predetermined value Vg, said polarized light excites transverse plasmon resonance in said graphene micro-ribbons, thus increasing light absorption, and producing a plasmon-enhanced photodetection signal obtained at said drain terminal.

7. The plasmon-enhanced terahertz graphene-based photodetector of claim 6 , wherein said Vg is approximately 6.5 V and below.

8. The plasmon-enhanced terahertz graphene-based photodetector of claim 1 , wherein said substrate is made from SiC (0001) material.

9. The plasmon-enhanced terahertz graphene-based photodetector of claim 1 , wherein the width of each said graphene micro-ribbons ranges from 0.6 μm to 1.1 μm.

10. The plasmon-enhanced terahertz graphene-based photodetector of claim 1 , wherein said graphene micro-ribbons extend substantially in parallel each to the other with a spacing therebetween not exceeding 2 μm.

11. The plasmon-enhanced terahertz graphene-based photodetector of claim 1 , wherein said angled relationship between said graphene micro-ribbons and said electrode lines is determined by an angle of approximately 45° therebetween.

12. The plasmon-enhanced terahertz graphene-based photodetector of claim 1 , wherein the length of each of said graphene micro-ribbons does not exceed 7.3 μm.

13. The plasmon-enhanced terahertz graphene-based photodetector of claim 1 , wherein each of said electrode lines are formed by at least two layers formed by different metals.

14. The plasmon-enhanced terahertz graphene-based photodetector of claim 13 , wherein said at least two layers of each said electrode line include a first layer formed from chromium and a second layer formed from gold, extending in contact each with the other along the length of said each electrode line.

15. The plasmon-enhanced terahertz graphene-based photodetector of claim 14 , wherein the thickness of said first layer of chromium is approximately 20 nm, and the thickness of said second layer of gold is approximately 25 nm.

16. The method of fabrication of a plasmon-enhanced terahertz graphene-based photodetector, comprising:
(a) patterning, on a surface of a SiC substrate, a single layer of graphene, thus forming an array of graphene micro-ribbons extending substantially in parallel each to the other,
(b) forming, in electrical contact with said array of graphene micro-ribbons, an array of bi-metallic electrode lines extending at an angle of approximately 45° relative to said graphene micro-ribbons,
(c) forming source and drain terminals at the outermost bi-metallic electrode lines of said array thereof,
(d) forming a gate terminal,
(e) applying a layer of electrolyte atop of said array of bi-metallic electrode lines to envelope and being in contact with said array of micro-ribbons and said array of bi-metallic electrode lines, said layer of electrolyte being coupled to the gate terminal, and
(f) coupling a source of gate voltage between said source and gate terminals.

17. The method of claim 16 , wherein in said step (a), said graphene micro-ribbons are formed by electron beam lithography followed by oxygen plasma treatment, and
wherein in said step (b), said bi-metallic electrode lines are formed by tilted-angle shadow evaporation technique.

18. The method of claim 16 , wherein said substrate is made of semi-insulating 6H—SiC material, and
said graphene micro-ribbons are patterned in an epitaxial single layer graphene.

19. The method of claim 16 , wherein said electrolyte is LiClO 4 :PEO having the ratio of 0.12:1.

20. The method of claim 16 , further comprising:
exposing said photodetector to an incident light polarized in a direction perpendicular to microsized elements selected from a group consisting of: said graphene micro-ribbons, said bi-metallic electrode lines, and combination thereof, to excite transverse plasmon resonance,
increasing said gate voltage to approximately 6.5 V relative to graphene's charge neutrality point, and
obtaining the photo response at said drain terminal.

Assignees

• Univ Maryland
• Us Navy
• Univ Monash

Inventors

• Cai Xinghan
• Sushkov Andrei B
• Jadidi Mohammad M
• Gaskill David Kurt
• Murphy Thomas E
• Fuhrer Michael
• Drew Howard Dennis

Classifications

• H01L31/022408

  Electricity · mapped topic

• H01L29/1606

  Electricity · mapped topic

• H01S4/00

  Devices using stimulated emission of electromagnetic radiation in wave ranges other than those covered by groups H01S1/00, H01S3/00 or H01S5/00, e.g. phonon masers, X-ray lasers or gamma-ray lasers · CPC title

• H01L31/02327

  Electricity · mapped topic

• G02B5/3058

  comprising electrically conductive elements, e.g. wire grids, conductive particles · CPC title