Light emitting device having light extraction structure
View Patent ↗A nitride-based light emitting device capable of achieving an enhancement in emission efficiency and an enhancement in reliability is disclosed. The light emitting device includes a semiconductor layer, and a light extracting layer arranged on the semiconductor layer and made of a material having a refractive index equal to or higher than a reflective index of the semiconductor layer.
1. A light emitting device comprising:
a conductive support structure;
a first electrode over the conductive support structure;
a semiconductor layer over the first electrode;
a light extracting structure arranged over the semiconductor layer; and
a second electrode over the semiconductor layer,
wherein the light extracting structure has a plurality of holes or grooves,
wherein a transparent material that is different from a material of the light extracting structure is located in the holes or grooves,
and wherein the refractive index of the light extracting structure is greater or less than the refractive index of the transparent material.
2. The light emitting device according to claim 1 , wherein the plurality of holes or grooves are regularly distributed.
3. The light emitting device according to claim 1 , further comprising:
a transparent conducting layer between the light extracting structure and the semiconductor layer.
4. The light emitting device according to claim 3 , wherein the transparent conducting layer has a thickness of λ/16n to λ/2n (where “λ” represents a wavelength of emitted light and “n” represents a refractive index of the transparent conducting layer).
5. The light emitting device according to claim 1 , further comprising:
a transparent metal layer between the light extracting structure and the semiconductor layer.
6. The light emitting device according to claim 5 , wherein the transparent metal layer comprises Ni and/or Au, or an alloy containing Ni and Au.
7. The light emitting device according to claim 1 , wherein the light extracting structure comprises an oxide or a nitride.
8. The light emitting device according to claim 1 , wherein the refractive index of the light extracting structure is 2.4 or more.
9. The light emitting device according to claim 1 , wherein the light extracting structure comprises SiN or TiO 2 .
10. The light emitting device according to claim 1 , wherein the semiconductor layer comprises:
an n-type semiconductor layer;
an active layer arranged on the n-type semiconductor layer; and
a p-type semiconductor layer arranged on the active layer.
11. The light emitting device according to claim 10 , wherein the p-type semiconductor layer has a thickness of 30 to 500 nm.
12. The light emitting device according to claim 1 , wherein the light extracting structure comprises a dielectric layer.
13. The light emitting device according to claim 1 , wherein the light extracting structure has a thickness of 150 nm or more.
14. The light emitting device according to claim 1 , wherein the semiconductor layer comprises:
a p-type semiconductor layer;
an active layer arranged on the p-type semiconductor layer; and
an n-type semiconductor layer arranged on the active layer.
15. The light emitting device according to claim 1 , wherein the first electrode comprises:
a reflective electrode; and
an ohmic electrode arranged on the reflective electrode.
16. The light emitting device according to claim 1 , wherein the conductive support structure comprises a metal or a semiconductor.
17. The light emitting device according to claim 1 , wherein the transparent material comprises an oxide.
18. The light emitting device according to claim 17 , wherein the transparent material comprises a transparent conducting oxide.
19. The light emitting device according to claim 1 , wherein the light extracting structure is formed on the semiconductor layer.
20. The light emitting device according to claim 1 , wherein the light extracting structure is formed by etching the semiconductor layer.
21. The light emitting device according to claim 1 , wherein the radius of hole or the groove is in the range of 0.1a to 0.45a, where “a” is an average distance between adjacent holes or grooves.
22. The light emitting device according to claim 1 , wherein the average distance between adjacent holes or grooves is in the range of 200nm to 5,000 nm.
23. The light emitting device according to claim 22 , wherein the depth of the hole or the groove is in the range of 0.25λ/n to 10λ/n, where “λ” represents the wavelength of emitted light and “n” represents the refractive index of the light extracting structure.
24. The light emitting device according to claim 22 , wherein the holes or grooves have a depth configured to saturate the extraction efficiency of the light extracting structure.