Light-emitting device
View Patent ↗A light-emitting device of the present invention includes: a semiconductor layer 1 including a light-emitting layer 12 ; a recess/projection portion 14 including recesses and projections formed in a pitch larger than a wavelength of light emitted from the light-emitting layer 12 , the recess/projection portion 14 being formed in a whole area or a partial area of the surface of the semiconductor layer which light is emitted from; and a reflective layer formed on an opposite surface of the semiconductor layer to the surface from which light is emitted, the reflective layer having a reflectance of 90% or more. According to the light-emitting device having such arrangement, the light can be emitted efficiently by synergetic effect of the reflective layer and the recess/projection portion.
1. A light-emitting device comprising:
a semiconductor layer comprising
a light-emitting layer;
a recess/projection portion including recesses and projections formed in a pitch larger than a wavelength of light emitted from the light-emitting layer, the recess/projection portion being formed in a whole area or a partial area of the surface of the semiconductor layer which light is emitted from; and
a reflective layer formed on an opposite surface of the semiconductor layer to the surface from which light is emitted, the reflective layer having a reflectance of 90% or more,
wherein the semiconductor layer includes a GaN system material, and the reflective layer includes an alloy containing silver as a primary element, wherein the reflective layer is in ohmic contact with the semiconductor.
2. The light-emitting device according to claim 1 , wherein the recesses and projections of the recess/projection portion are formed periodically or randomly.
3. The light-emitting device according to claim 1 , wherein the recess/projection portion has a shape acting as a lens.
4. The light-emitting device according to claim 3 , wherein the shape acting as a lens is a shape of Fresnel lens.
5. The light-emitting device according to claim 1 , wherein the reflective layer includes:
a conductive oxide layer formed above a surface of the semiconductor layer;
a metal layer formed on the conductive oxide layer, the metal layer consisting of silver, aluminum, a silver alloy containing silver as a primary element, or an aluminum alloy containing aluminum as a primarily element; and
a platinum layer formed between the semiconductor layer and the conductive oxide layer, the platinum layer having a mesh-like shape or an island-like shape.
6. The light-emitting device according to claim 1 , wherein the reflective layer includes a DBR.
7. The light-emitting device according to claim 1 , wherein the reflective layer includes:
a metal layer consisting of aluminum, silver, or a silver alloy containing silver as a primary element; and
a DBR formed on the metal layer.
8. The light-emitting device according to claim 7 , wherein each of the layers constituting the DBR has such a thickness as to allow light rays emitted from the light-emitting layer and having a high intensity range and coming at an angular range of a low transmissivity to reflect on the reflective layer at an increased reflectance.
9. The light-emitting device according to claim 1 , wherein the reflective layer includes:
a conductive oxide layer formed above a surface of the semiconductor layer;
a DBR layered on the conductive oxide layer;
a metal layer formed on the DBR layer and consisting of silver, aluminum, a silver alloy containing silver as a primary element, or an aluminum alloy containing aluminum as a primary element; and
a platinum layer formed between the semiconductor layer and the conductive oxide layer, and having a mesh-like shape or an island-like shape.
10. The light-emitting device according to claim 9 , wherein the DBR has a mesh-like shape or an island-like shape.
11. The light-emitting device according to claim 1 , wherein the reflective layer includes a photonic crystal.
12. The light-emitting device according to claim 1 , wherein a distance between a bottom plane of the recess/projection portion and an opposite surface of the semiconductor layer to the recess/projection portion is within several folds longer than a wavelength of light emitted from the light-emitting layer and traveling in the semiconductor layer.
13. The light-emitting device according to claim 1 , wherein the reflective layer serves as a p-type electrode, further comprising an n-type electrode formed on a surface of the semiconductor layer and having a reflectance of 80% or more, and being operable to associate with the p-type electrode.
14. The light-emitting device according to claim 13 , wherein the n-type electrode includes:
a conductive oxide layer formed on the surface of the semiconductor layer;
a metal layer formed on the conductive oxide layer and consisting of silver, aluminum, a silver alloy containing silver as a primary element, or an aluminum alloy containing aluminum as a primary element; and
a platinum layer formed between the semiconductor layer and the conductive oxide layer, the platinum layer having a mesh-like shape or an island-like shape.
15. The light-emitting device according to claim 13 , wherein the n-type electrode includes:
a conductive oxide layer formed on the surface of the semiconductor layer;
a DBR formed on the conductive oxide layer;
a metal layer formed on the DBR and consisting of silver, aluminum, a silver alloy containing silver as a primary element, or an aluminum alloy containing aluminum as a primary element; and
a platinum layer formed between the semiconductor layer and the conductive oxide layer, the platinum layer having a mesh-like shape or an island-like shape.
16. The light-emitting device according to claim 15 , wherein the DBR has a mesh-like shape or an island-like shape.
17. The light-emitting device according to claim 1 , further comprising a wavelength converting layer formed on a light-extraction surface of the semiconductor layer and adapted for converting the wavelength of light rays emitted from the semiconductor layer and irradiating the same.
18. The light-emitting device according to claim 1 , wherein said device has a light extraction efficiency of 55% or more.
19. A method for producing a light-emitting device, comprising:
a semiconductor layer comprising
a light-emitting layer, and
a recess/projection portion including recesses and projections formed in a pitch larger than a wavelength of light emitted from the light-emitting layer, the recess/projection portion being formed on a whole area or a partial area of the surface of the semiconductor layer from which light is emitted;
a wavelength converting layer formed on a light-extraction surface of the semiconductor layer and adapted for converting the wavelength of light rays emitted from the semiconductor layer and irradiating the same; and
a reflective layer formed on an opposite surface of the semiconductor layer to the surface from which light is emitted, the reflective layer having a reflectance of 90% or more, the method comprising:
depositing a material having a refractive index which is substantially the same as that of the semiconductor layer to form the recess/projection portion, and
forming a wavelength converting layer on a light-extraction surface of the semiconductor layer wherein the reflective layer is in ohmic contact with the semiconductor.
20. A light-emitting device comprising:
a semiconductor layer comprising
a light-emitting layer, and
a recess/projection portion including recesses and projections formed in a pitch larger than a wavelength of light emitted from the light-emitting layer, the recess/projection portion being formed in a whole area or a partial area of the surface of the semiconductor layer which light is emitted from; and
a reflective layer formed on an opposite surface of the semiconductor layer to the surface from which light is emitted, the reflective layer having a reflectance of 95% or more, wherein the semiconductor layer includes a GaN system material, and said reflective layer includes:
a conductive oxide layer formed on a surface of the semiconductor layer;
a metal layer formed on the conductive oxide layer, the metal layer comprising an alloy containing silver as a primary element; and
a platinum layer formed between the semiconductor layer and the conductive oxide layer, the platinum layer having a mesh-like shape or an island-like shape wherein the reflective layer is in ohmic contact with the semiconductor.
21. The light-emitting device according to claim 20 , wherein said device has a light extraction efficiency of 77% or more.