Light absorption and filtering properties of vertically oriented semiconductor nano wires

• US 9,000,353 B2
• Filed: 10/22/2010
• Issued: 04/07/2015
• Est. Priority Date: 06/22/2010
• Status: Expired due to Fees

• Current Assignee: President and Fellows of Harvard College (Harvard Corporation), Zena Technologies, Inc.
• Original Assignee: President and Fellows of Harvard College (Harvard Corporation), Zena Technologies, Inc.
• Inventors: Wober, Munib, Steinvurzel, Paul, Schonbrun, Ethan, Dan, Yaping, Crozier, Kenneth B., Seo, Kwanyong
• Primary Examiner(s): Ko, Tony
• Application Number:
  US12/910,664
• Publication Number:
  US 20110309237A1
• Time in Patent Office: 1,628 Days
• Field of Search: 250/208.1, 250/208.2
• US Class Current: 250/226
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: B82Y 99/00 Subject matter not provided for in other groups of this subclass
• CPC Class Codes: F21V 9/08 for producing coloured light, e.g. monochromatic; for reducing intensity of light with provision for controlling the colour F21V9/40
• CPC Class Codes: G02B 5/22 Absorbing filters G02B5/201 - G02B5/208 take precedence
• CPC Class Codes: G09F 13/00 Illuminated signs; Luminous advertising G09F9/00, G09F11/00 take precedence; control of displays in general using static means to present variable information G09G
• CPC Class Codes: H01L 27/1446 in a repetitive configuration
• CPC Class Codes: H01L 27/14603 Special geometry or disposition of pixel-elements, address-lines or gate-electrodes
• CPC Class Codes: H01L 27/14607 Geometry of the photosensitive area
• CPC Class Codes: H01L 27/14629 Reflectors
• CPC Class Codes: H01L 27/14692 Thin film technologies, e.g. amorphous, poly, micro- or nanocrystalline silicon
• CPC Class Codes: H01L 31/035227 the quantum structure being quantum wires, or nanorods carbon nanotubes H10K85/211
• CPC Class Codes: H01L 31/107 the potential barrier working in avalanche mode, e.g. avalanche photodiodes
• CPC Class Codes: H01L 31/18 Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
• CPC Class Codes: Y10S 977/762 Nanowire or quantum wire, i.e. axially elongated structure having two dimensions of 100 nm or less
• CPC Class Codes: Y10S 977/888 Shaping or removal of materials, e.g. etching
• CPC Class Codes: Y10S 977/954 Of radiant energy
• CPC Class Codes: Y10T 428/24174 including sheet or component perpendicular to plane of web or sheet
• CPC Class Codes: Y10T 428/24893 including particulate material

Abstract

A nanowire array is described herein. The nanowire array comprises a substrate and a plurality of nanowires extending essentially vertically from the substrate; wherein: each of the nanowires has uniform chemical along its entire length; a refractive index of the nanowires is at least two times of a refractive index of a cladding of the nanowires. This nanowire array is useful as a photodetector, a submicron color filter, a static color display or a dynamic color display.

Claims

1. A nanowire array, comprising a substrate and a plurality of nanowires extending essentially perpendicularly from the substrate;

wherein the nanowire array is operable as a color filter or the nanowires do not substantially couple;

wherein each of the nanowires has an essentially uniform chemical composition from one end of the nanowire to an opposite end of the nanowire in a longitudinal direction of the nanowire;

wherein a ratio of a radius of the nanowires to a pitch of the nanowires is at most 0.5.

2. The nanowire array of claim 1, wherein the nanowires do not substantially couple.

3. A nanowire array of claim 1;

wherein;

a refractive index of the nanowires is at least two times of a refractive index of a cladding of the nanowires.

4. A nanowire array of claim 1, wherein a number density of the nanowires is at most about 1.8/μ

².

5. The nanowire array of claim 1, wherein each of the nanowires is single crystalline, multi-crystalline or amorphous.

6. The nanowire array of claim 1, wherein the nanowires are composed of a semiconductor.

7. The nanowire array of claim 1, wherein the nanowires comprise one or more materials selected from the group consisting of Si, Ge, GaN, GaAs, SiO₂, and Si₃N₄.

8. The nanowire array of claim 1, wherein radii of the nanowires are from 10 to 1000 nm;

lengths of the nanowires are from 0.01 to 10 μ

m.

9. The nanowire array of claim 1, wherein the nanowires and the substrate have substantially the same chemical composition.

10. The nanowire array of claim 1, wherein the nanowires and the substrate are single crystalline and the lattices of the nanowires and the lattice of the substrate are continuous at interfaces therebetween.

11. The nanowire array of claim 1, wherein the nanowires are arranged in a predetermined pattern.

12. The nanowire array of claim 1, wherein a distance of a nanowire to a nearest neighbor of the nanowire along a direction parallel to the substrate is at least 800 nm.

13. The nanowire array of claim 1, wherein a reflectance spectrum thereof has a dip;

the dip position shifts to shorter wavelength with decreasing radii of the nanowires; and

the dip position is independent from a distance of a nanowire to a nearest neighbor of the nanowire along a direction parallel to the substrate.

14. The nanowire array of claim 1, wherein a reflectance spectrum thereof is independent from incident angles of illumination.

15. A method of fabricating the nanowire array of claim 1, comprising:

generating a pattern of dots in a resist layer using a lithography technique;

forming the nanowires by etching the substrate;

wherein shapes and sizes of the dots determine the cross-sectional shapes and sizes of the nanowires.

16. The method of claim 15, further comprising:

coating the substrate with the resist layer;

developing the pattern in the resist layer;

depositing a mask layer;

lifting off the resist layer; and

optionally removing the mask player.

17. The method of claim 15, wherein the etching is dry etching.

18. A method using the nanowire array of claim 1 as a photodetector comprises:

shining light on the nanowire array;

measuring photocurrent on the nanowires;

measuring photocurrent on the substrate;

comparing the photocurrent on the nanowires to the photocurrent on the substrate.

19. A method using the nanowire array of claim 1 as a static color display comprises:

determining locations and radii of the nanowires from an image to be displayed;

fabricating the nanowires with the determined radii at the determined locations on the substrate;

shining white light on the nanowire array.

20. A color filter comprising the nanowire array of claim 1, wherein each nanowire is placed on a photodetector, wherein only incident light with wavelengths in a dip of a reflectance spectrum of each nanowire is allowed reach the photodetector below.

21. A method using the color filter of claim 20 comprises shining white light on the nanowire array, detecting transmitted light below the nanowires.

22. The nanowire array of claim 1, wherein the nanowires are composed of an electrically insulating material.

23. The nanowire array of claim 1, wherein the nanowire array is operable as a submicron color filter.

24. A dynamic color display comprises a nanowire array comprising a substrate and a plurality of nanowires extending essentially perpendicularly from the substrate, the nanowire array being operable as a color filter;

an array of independently addressable white light sources on a side of the substrate opposite the nanowires, wherein each white light source corresponds to and is aligned in the substrate plane with one of the nanowires.

25. The dynamic color display of claim 24, wherein the white light sources are white LEDs or a scanning white light beam.

26. The dynamic color display of claim 24, wherein a first group of the nanowires have a first radius, a second group of the nanowires have a second radius, and a third group of the nanowires have a third radius, wherein the first group of the nanowires only allow red light to pass, the second group of the nanowires only allow green light to pass, and the third group of the nanowires only allow blue light to pass.

27. A nanowire array, comprising a substrate and a plurality of nanowires extending essentially perpendicularly from the substrate;

wherein the nanowire array is operable as a light filter or the nanowires do not substantially couple;

wherein at least one nanowire among the plurality of nanowires has a dip in a reflectance spectrum of the at least one nanowire, wherein a light of a wavelength in the dip incident on the at least one nanowire is guided by the at least one nanowire to be transmitted through the substrate;

wherein a ratio of a radius of the nanowires to a pitch of the nanowires is at most 0.5.

28. The nanowire array of claim 27, wherein the dip is at an IR wavelength.

29. The nanowire array of claim 27, wherein the nanowire array is operable as an infrared light filter.

30. The nanowire array of claim 27, wherein the at least one nanowire comprises GaAs.

31. The nanowire array of claim 27, wherein the at least one nanowire has a diameter of between about 70 nm and about 500 nm.

32. A dynamic display comprises the nanowire array of claim 27.

33. A photodetector comprising the nanowire array of claim 27.

34. The nanowire array of claim 27, wherein the nanowire array is operable as a light filter.

35. The nanowire array of claim 27, wherein the nanowires do not substantially couple.