Nanowire photo-detector grown on a back-side illuminated image sensor
View Patent ↗An embodiment relates to a device comprising a substrate having a front side and a back-side that is exposed to incoming radiation, a nanowire disposed on the substrate and an image sensing circuit disposed on the front side, wherein the nanowire is configured to be both a channel to transmit wavelengths up to a selective wavelength and an active element to detect the wavelengths up to the selective wavelength transmitted through the nanowire.
1. A waveguide comprising a substrate, at least one upstanding nanowire protruding from the substrate, and a vertical photogate covering a lateral surface of the at least one upstanding nanowire; wherein the at least one upstanding nanowire comprises a pn-junction or a pin-junction; wherein the nanowire has a first effective refractive index, n w and a material surrounding at least a portion of the nanowire to form a cladding has a second effective refractive index, n c , and the first refractive index is larger than the second refractive index, n w >n c configured to create waveguiding properties of the waveguide.
2. The waveguide according to claim 1 , wherein a shell-like structure encloses the nanowire or portion thereof.
3. The waveguide according to claim 1 , wherein the waveguide forms a defined angle with the substrate and the defined angle between nanowire and substrate is selected to create a vertical or close to vertical orientation.
4. The waveguide according to claim 1 , wherein the waveguide is provided with at least one cladding layer.
5. The waveguide according to claim 4 , wherein the one cladding layer is an optical cladding layer configured to enhance wave-guiding properties of the waveguide.
6. The waveguide according to claim 4 , wherein a plurality of cladding layers provide a graded refractive index towards a boundary of the nanowire.
7. The waveguide according to claim 4 , wherein the cladding layer comprises a metal to create electrical connection.
8. The waveguide according to claim 1 , wherein an active region is arranged within the nanowire.
9. The waveguide according to claim 8 , wherein the pn junction or the pin-junction is formed by doping the nanowire.
10. The waveguide according to claim 1 , wherein the nanowire is arranged to direct light in downward direction towards the substrate.
11. The waveguide according to claim 1 , comprising a planar photodetector under the at least one nanowire.
12. The waveguide according to claim 1 , wherein the nanowire is configured to detect infrared light.
13. The waveguide according to claim 1 , further comprising a filter that allows passage of infrared light but not visible light.
14. The waveguide according to claim 1 , wherein the nanowire comprises GaAs.
15. The waveguide according to claim 11 , wherein the planar photodetector is configured to detect infrared light.
16. The waveguide according to claim 11 , wherein the planar photodetector comprises GaAs.