Semiconductor light emitting device

1. A semiconductor light emitting device comprising:

a first conductive semiconductor layer;

an active layer on the first conductive semiconductor layer;

a second conductive semiconductor layer on the active layer;

a first electrode under the first conductive semiconductor layer, the first electrode comprising patterns having a predetermined shape;

a nitride semiconductor layer between the patterns of the first electrode; and

a first undoped semiconductor layer under the nitride semiconductor layer and the first electrode,

wherein a top surface of the first electrode physically contacts a lower surface of the first conductive semiconductor layer,

wherein a portion of the nitride semiconductor layer is disposed between side surfaces of the first electrode,

wherein the first conductive semiconductor layer is disposed between the first electrode and the active layer,

wherein the first electrode is disposed between the first undoped semiconductor layer and the first conductive semiconductor layer, and

wherein the first electrode physically contacts the first undoped semiconductor layer and the first conductive semiconductor layer.

2. The semiconductor light emitting device as claimed in claim 1 , wherein the nitride semiconductor layer comprises an undoped semiconductor layer.

3. The semiconductor light emitting device as claimed in claim 1 , wherein the nitride semiconductor layer comprises a group III-V compound semiconductor layer doped with first conductive dopant.

4. The semiconductor light emitting device as claimed in claim 3 , further comprising a substrate under the first undoped semiconductor layer, wherein the first undoped semiconductor layer is disposed between the substrate and the first electrode.

5. The semiconductor light emitting device as claimed in claim 1 , comprising a first electrode pad electrically connected to a top of the patterns of the first electrode and disposed on a portion of the first electrode.

6. The semiconductor light emitting device as claimed in claim 1 , wherein the first electrode comprises at least one of a linear pattern, a curve pattern, a linear-curve pattern, a branch pattern branching from one pattern, a polygonal pattern, a lattice pattern, a dot pattern, a lozenge pattern, a parallelogrammic pattern, a mesh pattern, a stripe pattern, a cross pattern, a radial pattern, a circular pattern, and a mixed pattern thereof.

7. A semiconductor light emitting device comprising:

a light emitting structure comprising a plurality of compound semiconductor layers;

a first electrode having a plurality of branches under the light emitting structure;

a nitride semiconductor layer disposed between branches of the first electrode and under the light emitting structure;

a substrate disposed under the first electrode and the nitride semiconductor layer;

a first electrode pad electrically connected to the first electrode; and

a second electrode on the light emitting structure, wherein the light emitting structure comprises:

a first conductive semiconductor layer electrically connected to the first electrode;

a second conductive semiconductor layer electrically connected to the second electrode; and

an active layer between the first conductive semiconductor layer and the second conductive semiconductor layer,

wherein the first conductive semiconductor layer is disposed between the first electrode and the active layer,

wherein a top surface of the first electrode physically contacts a lower surface of the first conductive semiconductor layer,

wherein the first electrode is disposed between the substrate and the first conductive semiconductor layer and physically contacts a top surface of the substrate and the first conductive semiconductor layer,

wherein the nitride semiconductor layer physically contacts the top surface of the substrate and the first conductive semiconductor layer,

wherein the nitride semiconductor layer comprises an undoped semiconductor layer disposed between the plurality of branches of the first electrode, and

wherein the substrate includes an insulating material.

8. The semiconductor light emitting device as claimed in claim 7 , wherein the nitride semiconductor layer comprises a group III-V compound semiconductor layer doped with first conductive dopant.

9. The semiconductor light emitting device as claimed in claim 8 , wherein the second electrode has at least one branch, and the first and second electrodes comprise at least one of a linear pattern, a curve pattern, a linear-curve pattern, a branch pattern branching from one pattern, a polygonal pattern, a lattice pattern, a dot pattern, a lozenge pattern, a parallelogrammic pattern, a mesh pattern, a stripe pattern, a cross pattern, a radial pattern, a circular pattern, and a mixed pattern thereof.

10. The semiconductor light emitting device as claimed in claim 1 , wherein the first electrode includes a transmissive material.

11. The semiconductor light emitting device as claimed in claim 1 , wherein the first electrode has a work function of 3 eV or above.

12. The semiconductor light emitting device as claimed in claim 1 , wherein the first electrode has a length equal to a width of a lower surface of the first conductive semiconductor layer.

13. The semiconductor light emitting device as claimed in claim 4 ,

wherein one of the side surfaces of the first electrode physically contacts an inner side of the nitride semiconductor layer, and

wherein the nitride semiconductor layer physically contacts the first conductive semiconductor layer and the first undoped semiconductor layer.

14. The semiconductor light emitting device as claimed in claim 13 , further comprising a first electrode pad physically contacting the top surface of the first electrode and a top surface of the nitride semiconductor layer.

15. The semiconductor light emitting device as claimed in claim 1 , wherein the nitride semiconductor layer has a thickness equal to that of the first electrode.

16. A semiconductor light emitting device comprising:

a light emitting structure comprising:

a first conductive semiconductor layer;

a second conductive semiconductor layer; and

an active layer between the first conductive semiconductor layer and the second conductive semiconductor layer;

a substrate under the first conductive semiconductor layer;

a first nitride semiconductor layer between the substrate and the first conductive semiconductor layer;

a first electrode having a plurality of branches between the substrate and the first conductive semiconductor layer;

a second nitride semiconductor layer between the substrate and the first nitride semiconductor layer; and

a second electrode contacted to the second conductive semiconductor layer,

wherein a top surface of the first electrode physically contacts a lower surface of the first conductive semiconductor layer,

wherein a side surface of the first electrode physically contacts an inner side of the first nitride semiconductor layer,

wherein a lower surface of the first electrode physically contacts an inner side of the second nitride semiconductor layer, and

wherein at least one of the first and second nitride semiconductor layers is formed as an undoped semiconductor layer.

17. The semiconductor light emitting device as claimed in claim 4 , wherein the first conductive semiconductor layer includes an n-type semiconductor layer and the second conductive semiconductor layer includes a p-type semiconductor layer, and

wherein the first electrode includes a metallic material.

18. The semiconductor light emitting device as claimed in claim 7 , wherein the first conductive semiconductor layer includes an n-type semiconductor layer and the second conductive semiconductor layer includes a p-type semiconductor layer, and

wherein the first electrode includes a metallic material.