Quantum dots of group IV semiconductor materials

• US 7,358,525 B2
• Filed: 07/16/2004
• Issued: 04/15/2008
• Est. Priority Date: 08/02/2001
• Status: Expired due to Term

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: UltraDots, Inc. (Omnipv Incorporated)
• Inventors: Lee, Howard Wing Hoon
• Primary Examiner(s): JACKSON JR, JEROME
• Application Number:
  US10/892,946
• Publication Number:
  US 20050017260A1
• Time in Patent Office: 1,369 Days
• Field of Search: 257/22
• US Class Current: 257/22
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: G02B 2006/12097 Ridge, rib or the like
• CPC Class Codes: G02B 2006/12145 Switch
• CPC Class Codes: G02B 2006/12147 Coupler
• CPC Class Codes: G02B 2006/12159 Interferometer
• CPC Class Codes: G02B 2006/12195 Tapering
• CPC Class Codes: G02B 6/122 Basic optical elements, e.g. light-guiding paths
• CPC Class Codes: G02B 6/1225 comprising photonic band-gap structures or photonic lattices
• CPC Class Codes: G02F 1/01791 Quantum boxes or quantum dots
• CPC Class Codes: G02F 1/217 Multimode interference type
• CPC Class Codes: G02F 1/3515 All-optical modulation, gating, switching, e.g. control of a light beam by another light beam G02F1/353, G02F1/37, G02F1/39 take precedence
• CPC Class Codes: G02F 1/3517 using an interferometer
• CPC Class Codes: G02F 1/3521 using a directional coupler
• CPC Class Codes: G02F 1/3556 Semiconductor materials, e.g. quantum wells
• CPC Class Codes: G02F 1/365 in an optical waveguide structure G02F1/377, G02F1/395 take precedence
• CPC Class Codes: G02F 2/006 All-optical wavelength conversion
• CPC Class Codes: G02F 2202/32 Photonic crystals
• CPC Class Codes: G02F 2202/36 Micro- or nanomaterials
• CPC Class Codes: H01L 29/127 Quantum box structures
• CPC Class Codes: H01L 29/16 : including, apart from doping materials or other impurities, only elements of Group IV of the Periodic Table
• CPC Class Codes: H01L 29/1602 : Diamond
• CPC Class Codes: H01L 33/20 : with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/34 : containing only elements of Group IV of the Periodic Table
• CPC Class Codes: Y10S 977/814 : Group IV based elements and compounds, e.g. CxSiyGez, porous silicon

Abstract

The invention relates to a quantum dot. The quantum dot comprises a core including a semiconductor material Y selected from the group consisting of Si and Ge. The quantum dot also comprises a shell surrounding the core. The quantum dot is substantially defect free such that the quantum dot exhibits photoluminescence with a quantum efficiency that is greater than 10 percent.

Claims

1. A quantum dot comprising:

a) a core that is substantially crystalline and including Ge;

b) a shell that is inorganic and substantially noncrystalline and including GeO_n with n between approximately 1.5 and 2, said shell surrounding said core and having a thickness greater than one monolayer of GeO_n and up to ten monolayers of GeO_n; and

c) at least one surface ligand coupled to said shell,

said quantum dot being substantially defect free such that said quantum dot exhibits photoluminescence with a quantum efficiency that is at least 40 percent.

2. The quantum dot of claim 1, wherein a plurality of surface ligands are coupled to said shell to provide a surface coverage between approximately 50 percent and 100 percent.

4. The quantum dot of claim 1, wherein a plurality of surface ligands are coupled to said shell to provide a surface coverage between approximately 80 percent and 100 percent.

5. The quantum dot of claim 1, wherein said at least one surface ligand contains an atom selected from the group consisting of C, O, S, Si, N, P, and Se, and said shell forms a covalent bond with said atom.

6. The quantum dot of claim 1, wherein said at least one surface ligand is selected from the group consisting of alkyls, alkenyls, alkynyls, aromatics, aromatic heterocycles, conjugated aromatics, polyenes, cyanides, hydroxys, alkoxys, carboxylates, phenoxys, siloxys, cyanates, thioalkyls, thioaryls, thiocyanates, silylthios, substituted silyl groups, amino groups, mono-substituted amines, di-substituted amines. imino groups, and silylaminos.

7. The quantum dot of claim 1, wherein said core has a diameter between approximately 1 nm and 20 nm.

8. The quantum dot of claim 1, wherein said core has a diameter between approximately 1 nm and 50 nm.

9. The quantum dot of claim 1, wherein said core has a diameter between approximately 1 nm and 10 nm.

10. The quantum dot of claim 1, wherein said core is substantially spherical with an aspect ratio between approximately 0.8 and 1.2.

11. The quantum dot of claim 1, wherein n is between approximately 1.8 and 2.

12. The quantum dot of claim 1, wherein said shell completely surrounds said core.

13. The quantum dot of claim 1, wherein said quantum efficiency is at least 50 percent.

3. A population of quantum dots, comprising:

a plurality of quantum dots that each includes;

a) a core that is substantially crystalline and including Ge;

b) a ligand layer surrounding said core, said ligand layer including a plurality of surface ligands; and

c) a shell positioned between said core and said ligand layer and surrounding said core, said shell being inorganic and substantially noncrystalline and including GeO_n with n being between approximately 1.5 and 2, said shell having a thickness greater than one monolayer of GeO_n and up to ten monolayers of GeO_n,

said plurality of quantum dots being monodispersed with respect to sizes of said plurality of quantum dots,

said plurality of quantum dots being substantially defect free such that said plurality of quantum dots exhibits photoluminescence with a quantum efficiency that is greater than 10 percent.

14. The population of claim 3, wherein said plurality of surface ligands are coupled to said shell to provide a surface coverage between approximately 80 percent and 100 percent.

15. The population of claim 3, wherein a surface ligand of said plurality of surface ligands contains an atom selected from the group consisting of C, O, S, Si, N, P, and Se, and said shell forms a covalent bond with said atom.

16. The population of claim 3, wherein a surface ligand of said plurality of surface ligands is selected from the group consisting of alkyls, alkenyls, alkynyls, aromatics, aromatic heterocycles, conjugated aromatics, polyenes, cyanides, hydroxys, alkoxys, carboxylates, phenoxys, siloxys, cyanates, thioalkyls, thioaryls, thiocyanates, silylthios, substituted silyl groups, amino groups, mono-substituted amines, di-substituted amines, imino groups, and silylaminos.

17. The population of claim 3, wherein said sizes of said plurality of quantum dots exhibit less than a 10 percent root-mean-square deviation.

18. The population of claim 3, wherein said sizes of said plurality of quantum dots exhibit less than a 5 percent root-mean-square deviation.

19. The population of claim 3, wherein said plurality of quantum dots has a density of defects that is less than 1 defect per 1,000 quantum dots.

20. The population of claim 19, wherein said density of defects is less than 1 defect per 10⁶ quantum dots.

21. The population of claim 3, wherein n is between approximately 1.8 and 2.

22. The population of claim 3, wherein said quantum efficiency is at least 20 percent.

23. The population of claim 3, wherein said quantum efficiency is at least 50 percent.