Sub-wavelength antenna enhanced bilayer graphene tunable photodetector
The integration of bilayer graphene with an absorption enhancing sub-wavelength antenna provides an infrared photodetector capable of real-time spectral tuning without filters at nanosecond timescales.
1. A tunable photodetector, comprising:
a bilayer graphene layer;
a gate dielectric layer disposed on the frontside of the bilayer graphene layer;
a resonant sub-wavelength antenna top gate disposed on the gate dielectric layer, wherein the resonant sub-wavelength antenna top gate and the gate dielectric layer are adapted to amplify the absorption of incident light in the bilayer graphene layer by resonant surface mode coupling;
a conductive back gate disposed on the backside and insulated from the bilayer graphene layer for applying an electric field with the top gate across the bilayer graphene layer to tune a bandgap therein; and
a source and a drain disposed on the bilayer graphene layer with the gate dielectric layer therebetween, thereby forming a dual-gated field-effect transistor.
2. The tunable photodetector of claim 1 , wherein the bandgap is tunable from the mid-infrared to terahertz regime of the incident light.
3. The tunable photodetector of claim 1 , wherein the incident light has a wavelength greater than 5 microns.
4. The tunable photodetector of claim 1 , wherein the bilayer graphene layer comprises epitaxial graphene grown on a semi-insulating silicon carbide substrate.
5. The tunable photodetector of claim 4 , wherein the conductive back gate comprises a region of conductive ions implanted in the semi-insulating silicon carbide substrate.
6. The tunable photodetector of claim 5 , further comprising a back metal reflector on the back side of the ion-implanted semi-insulating silicon carbide substrate.
7. The tunable photodetector of claim 4 , wherein the conductive back gate comprises a highly doped silicon carbide substrate and wherein the semi-insulating substrate comprises an undoped silicon carbide layer grown on the highly doped silicon carbide substrate.
8. The tunable photodetector of claim 4 , wherein the semi-insulating silicon carbide substrate is back-thinned and a metal layer is deposited on the backside of the back-thinned silicon carbide substrate to provide the conductive back gate and a back metal reflector.
9. The tunable photodetector of claim 1 , wherein the sub-wavelength antenna comprises a conductive layer patterned with a periodic array of sub-wavelength apertures.
10. The tunable photodetector of claim 9 , wherein the sub-wavelength antenna comprises a frequency specific surface structure.
11. The tunable photodetector of claim 9 , wherein the periodic array of sub-wavelength apertures has a periodicity of less than one-third the wavelength of the incident light.
12. The tunable photodetector of claim 9 , wherein the periodic array of sub-wavelength apertures comprises a connected periodic loop-aperture geometry.
13. The tunable photodetector of claim 1 , wherein the gate dielectric layer comprises SiO 2 , Al 2 O 3 , Si 3 N 4 , or HfO 2 .
14. The tunable photodetector of claim 1 , wherein the thickness of the gate dielectric layer is less than 100 nanometers.
15. The tunable photodetector of claim 1 , wherein the conductive back gate provides a reflecting backplane that is coupled with the sub-wavelength antenna to further enhance absorption of the incident light in the bilayer graphene layer.
16. The tunable photodetector of claim 1 , further comprising a reflecting backplane disposed on the backside of the conductive back gate that is coupled with the sub-wavelength antenna to further enhance absorption of the incident light in the bilayer graphene layer.