STRUCTURED SUBSTRATE FOR LEDS WITH HIGH LIGHT EXTRACTION

• US 20150001568A1
• Filed: 01/04/2013
• Published: 01/01/2015
• Est. Priority Date: 01/05/2012
• Status: Active Grant

• Current Assignee: Commissariat a L'Energie Atomique (AES Corporation), Soitec S.A.
• Original Assignee: Commissariat A L'Energie Atomique et AUX Energies Alternatives, Soitec S.A.
• Inventors: Desieres, Yohan, Gilet, Philippe, Guenard, Pascal
• Granted Patent: US 9,412,904 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: G02B 5/0236 the diffusion taking place within the volume of the element
• CPC Class Codes: G02B 5/0284 used in reflection
• CPC Class Codes: H01L 2933/0025 relating to coatings
• CPC Class Codes: H01L 2933/0058 relating to optical field-shaping elements
• CPC Class Codes: H01L 33/005 Processes
• CPC Class Codes: H01L 33/10 with a light reflecting structure, e.g. semiconductor Bragg reflector
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector

Abstract

A device for back-scattering an incident light ray, including: a host substrate; a structured layer; a first face in contact with a front face of the host substrate; a second flat face parallel to the first face; a first material and a second material which form, in a mixed plane, alternating surfaces at least one of whose dimensions is between 300 nm and 800 nm, the mixed plane is between the first and second face of the structured layer; wherein the refractive index of the first and of the second material are different, the structured layer is covered by a specific layer, the specific layer is made of a material which is different from the first and second materials of the structured layer, and the specific layer is crystalline and semi-conductive.

Claims

1-28. -28. (canceled)

29. A device for back-scattering of an incident light ray, comprising:

a host substrate;

a structured layer;

a first face in contact with a front face of the host substrate;

a second flat face which is parallel or substantially parallel to the first face;

a first material A and a second material B, which form, in a mixed plane, alternating surfaces at least one of whose dimensions may be between 300 nm and 800 nm, wherein the mixed plane is between the first and second face of the structured layer;

wherein the refractive index of the first and of the second material are different;

wherein the structured layer is covered with a specific layer, the specific layer being made of a material C which is different from material A and from material B of the structured layer, wherein the specific layer is crystalline and semi-conductive, with a thickness of less than one micrometer, or less than 500 nm.

30. A device for back-scattering of an incident light-ray according to claim 29, wherein the difference in refractive index between the specific layer and the refractive index of the second material B is less than 30%.

31. A device for back-scattering of an incident light ray according to claim 29, wherein the specific layer comprises gallium nitride, or silicon carbide, or silicon, or indium gallium nitride.

32. A device for back-scattering of an incident light ray according to claim 29, wherein the first face and the second face of the structured layer are separated by a distance of between 50 nm and 500 nm.

33. A device for back-scattering of an incident light ray according to claim 29, wherein the refractive index of the first material A is less than the refractive index of the second material B, the refractive index of the first material A being less than or equal to 1.6.

34. A device for back-scattering of an incident light ray according to claim 29, wherein the second material is in contact with the specific layer.

35. A device for back-scattering of an incident light ray according to claim 29, wherein the first material A or the second material B absorb less than 30% of the light ray.

36. A device for back-scattering of an incident light ray according to claim 29, wherein the first material A and the second material B alternate in the mixed plane along one or two dimensions.

37. A device for back-scattering of an incident light ray according to claim 29, wherein the surfaces form amorphous or structured patterns, with dimensions of the surfaces being between 350 nm and 600 nm, or of an order of the wavelength of the incident light ray.

38. A device for back-scattering of an incident light ray according to claim 29, wherein plural mixed planes are in contact with and parallel to each other, to form a mixed volume in the structured layer.

39. A device for back-diffusion of an incident light-ray according to claim 38, the mixed volume comprising the first surface and/or the second surface of the structured layer.

40. A device for back-scattering of an incident light ray according to claim 29, wherein the first and/or the second material is titanium oxide, or tantalum oxide, or zinc oxide, or silica.

41. A device for back-scattering of an incident light ray according to claim 29, wherein a metallic layer or dielectric multi-layer is present between the host substrate and the structured layer and/or between the first and/or second material which make up the structured layer, wherein the thickness of this metallic layer and/or of the dielectric multi-layer is between a few nanometers and a few hundred nanometers or less than 150 nm or less than 100 nm.

42. A light emitting device comprising:

a device for back-scattering of an incident light ray according to claim 29,

a multi-layer structure of LED type, comprising a first crystalline layer formed on the specific layer, wherein lattice parameters of the first layer and of the specific layer are close or identical.

43. A light emitting device according to claim 42, wherein the first layer has a thickness of more than 500 nm, or of between 100 nm and 1 μ

m.

44. A light emitting device according to claim 42, wherein the multi-layer structure comprises an active layer which exhibits a thickness of less than 200 nm or 150 nm or 100 nm.

45. A light emitting device according to claim 44, wherein the first layer is n-type doped and wherein the multi-layer structure comprises a second crystalline p-type doped layer with the active layer separating the first and the second layers.

46. A light emitting device according to claim 45, wherein the first and second layers each comprise an electrical contact.

47. A light emitting device according to claim 45, wherein the multi-layer structure comprises a semi-conductive and semi-transparent layer which separates the second layer from its electrical contact.

48. A light emitting device according to claim 45, wherein the multi-layer structure comprises a hole-stopping layer between the first and second layers.

49. A light emitting device according to claim 42, wherein the first layer exhibits a composition which is close to or identical to a composition of the specific layer.

50. A light emitting device according to claim 42, wherein the incident light-ray is emitted by the light emitting device.

51. A method for manufacturing a device for back-scattering of incident light rays according to claim 29, comprising:

a) formation of a structured layer which exhibits a first face in contact with a front face of a host substrate, and a second flat face parallel or substantially parallel to the first face, where a) comprises;

a1) deposition of a first material A on the front face;

a2) deposition of a second material B so that the first material A and the second material B form, in a mixed plane, alternating surfaces at least one of whose dimensions is between 300 nm and 800 nm, wherein the mixed plane is between the first and second face of the structured layer, with refractive indices of the first material A and of the second material B being different;

b) transfer of a specific layer onto the second face of the structured layer, the specific layer being made of a material C which is different from material A and from material B of the structured layer, wherein the specific layer is crystalline and semi-conductive, with a thickness of less than a micrometer, or less than 500 nm.

52. A method for manufacture according to claim 51, wherein a) comprises a3) mechanical and/or chemical polishing of the structured layer, at the second face.

53. A method of manufacture according to claim 51, wherein a1) is followed by a removal of a portion of the first deposited material A so that its thickness is not homogeneous, and wherein a2) is carried out so that the second material B covers the remaining first material A.

54. A method of manufacture according to claim 51, wherein b) is carried out by a technique comprising a molecular adhesion.

55. A manufacturing method for a light emitting device according to claim 42, comprising formation by epitaxy of a first crystalline layer belonging to an LED-type multi-layer structure, on a specific layer belonging to a device for back-scattering of an incident light-ray.

56. A manufacturing method according to claim 55, comprising manufacturing a back-scattering device.