Highly reflective mounting arrangement for LEDs
View Patent ↗A semiconductor device emitting light about a predetermined wavelength comprising a structure comprising a plurality of layers, sometimes referred to as a stack, providing low resistance, high reflectivity and ohmic contacts to at least one semiconductor material.
1. A device capable of emitting light about a predetermined wavelength in response to an applied electric current comprising:
a substrate comprising first and second surfaces;
a light emitting portion comprising a semiconductor material and first and second surfaces wherein the light is emitted from the first and second surfaces and the second surface is substantially coupled to the first surface of the substrate;
a first layer coupled to the second surface of the substrate comprising an optically transmissive, dielectric layer with a refractive index less than the refractive index of the substrate and of a thickness greater than one-quarter wavelength of the predetermined wavelength divided by the index of refraction of the optically transmissive dielectric layer;
one or more second layers coupled to the first layer wherein each second layer comprises a first dielectric layer of high-index of refraction and a second dielectric layer of low-index of refraction wherein the first dielectric layer is of a thickness about mλ/4n H , and the second dielectric layer is of a thickness about kλ/4n L , where m and k are odd integers, λ is the predetermined nominal wavelength in air, n H is the refractive index of the high-index of refraction dielectric layer and n L is the refractive index of the low-index of refraction dielectric layer; and
a metallic layer coupled to the one or more second layers; wherein the reflectivity of the metallic layer to the predetermined wavelength is greater than about 50 percent.
2. The device of claim 1 wherein said metallic layer comprises at least three layers comprising:
a first layer comprising said metallic layer;
a second layer comprising a diffusion barrier; and
a third layer of a solderable material; wherein elements of the solderable material are prevented from reaching said metallic layer by the second layer.
3. The device of claim 1 wherein said optically transmissive, dielectric layer is chosen from a group consisting of silicon dioxide, silicon monoxide, MgF 2 and siloxane polymers.
4. The device of claim 1 wherein said high-index of refraction layer of said one or more second layers is chosen from a group consisting of titanium dioxide (TiO 2 ), Ti 3 O 5 , Ti 2 O 3 , TiO, [ZrO 2 +TiO 2 ZrO 2 Nb 2 O 5 ], CeO 2 , ZnS, Al 2 O 3 , niobium pentoxide (Nb 2 O 5 ), tantalum pentoxide (Ta 2 O 5 ) and siloxane polymers and said low-index of refraction layer of said one or more second layers is chosen from a group comprising SiO, SiO 2 , MgF 2 and siloxane polymers.
5. The device of claim 1 wherein said metallic layer is chosen from a group consisting of Al, Ag, Rh, Pd, Cu, Au, Cr, Ti, Ni, nickel/gold alloys, chrome/gold alloys, silver/aluminum mixtures and combinations thereof.
6. The device of claim 1 further comprising a metal-oxide layer coupled to said first surface of said light emitting portion wherein the metal-oxide layer comprises a first layer with an index of refraction greater than 2 and an optical loss factor less than 0.2.
7. The device of claim 6 wherein said metal-oxide layer is chosen from a group consisting of metal oxides, silicon carbide, GaN, Ta 2 O 5 , Nb 2 O 5 , TiO 2 , AlInGaN based solid solutions and their non-stoichiometric mixtures, and wherein said metal-oxide layer portion has a predetermined shape and pattern.
8. The device of claim 6 wherein said metal-oxide layer further comprises a second coating layer wherein the second coating layer portion has a three dimensional pattern chosen from a group consisting of ribs, cylinders, slots, polygon shaped ribs, triangular shaped ridges, hemispherical shaped mounds, horizontal cylindrical shaped ribs, cylinders, ellipsoids, hemispheres, rectilinear trenches, rectilinear solids, cones, angled cylinders, angled hemispheres, angled ellipsoids, angled rectilinear trenches, angled solids and angled cones and wherein element to element spacing may be uniform or not.
9. A device capable of emitting light about a predetermined wavelength in response to an applied electric current comprising:
a substrate comprising first and second surfaces;
a light emitting portion comprising a semiconductor material and first and second surfaces wherein the light is emitted from the first and second surfaces and the second surface is substantially coupled to the first surface of the substrate;
a first layer coupled to the second surface of the substrate comprising an optically transmissive, dielectric layer with a refractive index less than the refractive index of the substrate and of a thickness greater than one-quarter wavelength of the predetermined wavelength divided by the index of refraction of the optically transmissive dielectric layer;
one or more second layers coupled to the first layer wherein each second layer comprises a first dielectric layer of high-index of refraction and a second dielectric layer of low-index of refraction wherein the first dielectric layer is of a thickness about mλ/4n H , and the second dielectric layer is of a thickness about kλ/4n L , where m and k are odd integers, λ is the predetermined nominal wavelength in air, n H is the refractive index of the high-index of refraction dielectric layer and n L is the refractive index of the low-index of refraction dielectric layer;
a metal-oxide layer coupled to said first surface of the light emitting portion wherein the metal-oxide layer comprises a first layer with an index of refraction greater than 2 and an optical loss factor less than 0.2; and
a metallic layer coupled to the one or more second layers; wherein the reflectivity of the metallic layer to the predetermined wavelength is greater than about 50 percent.
10. The device of claim 9 wherein said metal-oxide layer further comprises a second coating layer wherein the second coating layer portion has a three dimensional pattern chosen from a group consisting of ribs, cylinders, slots, polygon shaped ribs, triangular shaped ridges, hemispherical shaped mounds, horizontal cylindrical shaped ribs, ellipsoids, hemispheres, rectilinear trenches, rectilinear solids, cones, angled cylinders, angled hemispheres, angled ellipsoids, angled rectilinear trenches, angled solids and angled cones and wherein element to element spacing may be uniform or not.