WAVELENGTH-SENSITIVE DETECTOR WITH ELONGATE NANOSTRUCTURES

• US 20100171025A1
• Filed: 10/06/2009
• Published: 07/08/2010
• Est. Priority Date: 07/29/2005
• Status: Active Grant

• Current Assignee: Interuniversitair Micro-Electronica Centrum VZW (IMEC International)
• Original Assignee: IMEC International
• Inventors: Verhulst, Anne S., Vandervorst, Wilfried
• Granted Patent: US 8,232,517 B2
• Time in Patent Office: Days
• US Class Current: 250/214.100
• CPC Class Codes: H01L 31/0352 characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions
• CPC Class Codes: H01L 31/09 Devices sensitive to infrared, visible or ultraviolet radiation H01L31/101 takes precedence
• CPC Class Codes: Y10S 977/954 Of radiant energy

Abstract

A wavelength-sensitive detector is provided that is based on elongate nanostructures, e.g. nanowires. The elongate nanostructures are parallel with respect to a common substrate and they are grouped in at least first and second units of a plurality of parallel elongate nanostructures. The elongate nanostructures are positioned in between a first and second electrode, the first and second electrodes lying respectively in a first and second plane substantially perpendicular to the plane of substrate, whereby all elongate nanostructures in a same photoconductor unit are contacted by the same two electrodes. Circuitry is added to read out electrical signals from the photoconductor units. The electronic density of states of the elongate nanostructures in each unit is different, because the material, of which the elongate nanostructures are made, is different or because the diameter of the elongate nanostructures is different. Each unit of elongate nanostructures therefore gives a different response to incident photons such that wavelength-specific information can be derived with the device.

Claims

1. A wavelength-sensitive detector comprising a first photoconductor unit and a second photoconductor unit on a substrate;

wherein a plane of the first photoconductor unit and a plane of the second photoconductor unit are substantially parallel to each other and are substantially perpendicular to a plane of the substrate;

wherein each photoconductor unit comprises a first electrode having a first longitudinal direction and a first sidewall lying in a first plane parallel with the first longitudinal direction and a second electrode having a second longitudinal direction and a second sidewall lying in a second plane parallel with said second longitudinal direction;

wherein the first photoconductor unit comprises a plurality of first type elongate nanostructures positioned in between the first electrode and the second electrode of the first photoconductor unit, the elongate nanostructures each having a longitudinal axis, wherein the longitudinal axes of the first type elongate nanostructures are substantially parallel to each other and are substantially perpendicular to a plane of the first electrode and a plane of the second electrode of the first photoconductor unit; and

wherein the second photoconductor unit comprises a plurality of second type elongate nanostructures positioned in between the first electrode and the second electrode of the second photoconductor unit, the elongate nanostructures each having a longitudinal axis, wherein the longitudinal axes of the second type elongate nanostructures are substantially parallel to each other and are substantially perpendicular to a plane of the first electrode and a plane of the second electrode of the second photoconductor unit, wherein the first type elongate nanostructures are different from the second type elongate nanostructures.

2. The wavelength-sensitive detector of claim 1, wherein the elongate nanostructures comprise a semiconducting material.

3. The wavelength sensitive detector of claim 1, wherein the elongate nanostructures comprise single walled carbon nanotubes.

4. The wavelength-sensitive detector of claim 1, wherein the elongate nanostructures in a photoconductor unit each have substantially the same diameter and each comprise a same material.

5. The wavelength-sensitive detector of claim 1, wherein the first type elongate nanostructures and the second type elongate nanostructures are different from each other in at least one of a material and a diameter.

6. The wavelength-sensitive detector of claim 1, wherein the elongate nanostructures in at least one of the first photoconductor unit and second photoconductor unit are partly n-type doped and partly p-type doped, such that the photoconductor unit comprises a pn diode.

7. The wavelength-sensitive detector of claim 1, wherein the elongate nanostructures within a photoconductor unit are stacked next to each other, on top of each other, or both next to each other and on top of each other.

8. The wavelength-sensitive detector of claim 1, wherein the first electrode and the second electrode each comprise a conductive material.

9. The wavelength-sensitive detector of claim 1, wherein the elongate nanostructures of a photoconductor unit have a diameter of from 0.3 nm to 300 nm.

10. The wavelength-sensitive detector of claim 9, wherein the elongate nanostructures of a photoconductor unit have a diameter from 0.3 nm up to 100 nm.

11. The wavelength-sensitive detector of claim 1, wherein the elongate nanostructures comprise at least one material selected from the group consisting of group IV materials, binary compounds of group IV materials, group III/V materials, binary compounds of group III/V materials, tertiary compounds of group III/V materials, quaternary compounds of group III/V materials, group II/VI materials, or binary compounds of II/VI materials, tertiary compounds of II/VI materials, and quaternary compounds of II/VI materials.

12. The wavelength-sensitive detector of claim 1, wherein the elongate nanostructures of a photoconductor unit have a doping profile.

13. The wavelength-sensitive detector of claim 1, wherein the elongate nanostructures of a photoconductor unit are embedded in a material which is transparent in a range of wavelengths to be detected.

14. The wavelength-sensitive detector of claim 1, wherein the first photoconductor unit is situated in between the substrate and the second photoconductor unit, and wherein the first type elongate nanostructures have a larger bandgap than the second type elongate nanostructures.

15. The wavelength-sensitive detector of claim 1, wherein the second photoconductor unit is situated on top of the first photoconductor unit, the second photoconductor unit comprising a plurality of second type elongate nanostructures oriented in a direction substantially perpendicular to a direction of the plurality of first type elongate nanostructures in the first photoconductor unit.

16. The wavelength-sensitive detector of claim 1, wherein the detector is configured to determine a frequency of incident radiation.

17. The wavelength-sensitive detector of claim 1, wherein the detector is configured to determine a polarization of incident radiation.

18. The wavelength-sensitive detector of claim 17, wherein the detector comprises at least a first photoconductor unit and a second photoconductor unit, the first photoconductor unit comprising first type elongate nanostructures oriented in a first direction and a second photoconductor unit comprising second type elongate nanostructures oriented in a second direction, wherein the first direction and the second direction are substantially perpendicular to each other.

19. The wavelength-sensitive detector of claim 1, wherein the detector is configured to convert an optical signal into an electrical signal and to determine a frequency of incident light at a same time.

20. The wavelength-sensitive detector of claim 1, wherein the detector is configured to represent one pixel of a color-sensitive camera.

21. A method for manufacturing a wavelength-sensitive detector comprising a first photoconductor unit and a second photoconductor unit on a substantially planar substrate, the method comprising:

providing a first photoconductor unit and a second photoconductor unit on a substrate, wherein providing a photoconductor unit comprises;

providing a first electrode having a first longitudinal direction and having a sidewall lying in a first plane parallel with said first longitudinal direction;

providing a second electrode having a second longitudinal direction and having a sidewall lying in a second plane parallel to the second longitudinal direction, wherein the first plane and the second plane are substantially parallel to each other and are substantially perpendicular to a plane of the substrate; and

providing a plurality of elongate nanostructures, each having a first end and a second end, wherein the first ends of the elongate nanostructures are attached to the sidewall of the first electrode, and wherein the second ends of the elongate nanostructures are attached to the sidewall of the second electrode, wherein each elongate nanostructure has a longitudinal axis, wherein the longitudinal axes of the elongate nanostructures are substantially parallel to each other and are substantially perpendicular to the first plane and the second plane;

wherein providing the first and second photoconductor units comprises providing a first photoconductor unit with a first type of elongate nanostructures and a second photoconductor unit with a second type of elongate nanostructures, wherein the first type of elongate nanostructures are different from the second type of elongate nano structures.

22. The method of claim 21, wherein the step of providing a plurality of elongate nanostructures comprises growing elongate nanostructures by chemical vapor deposition or pulsed laser deposition.

23. The method of claim 21, wherein the step of providing a plurality of elongate nanostructures comprises growing elongate nanostructures onto the sidewall of the first electrode.

24. The method of claim 21, comprising depositing catalyst particles onto the first sidewall of the first electrode, wherein the step of depositing is conducted before the step of growing a plurality of elongate nanostructures.

25. The method of claim 21, further comprising providing a transparent material in between the elongate nanostructures.

26. The method of claim 25, wherein the transparent material is a sacrificial material, the method further comprising removing the transparent material after manufacturing the photoconductor units.

27. The method of claim 21, further comprising adding additional signal-processing circuitry to each of the photoconductor units.