Light emitting device and manufacturing method thereof

1. A light emitting device, comprising:

a first conductive semiconductor layer;

an active layer on the first conductive semiconductor;

a second conductive semiconductor layer on the active layer;

a roughness layer, including a dot shape, on the second conductive semiconductor layer;

a third conductive semiconductor layer on the roughness layer; and

a second electrode on the third conductive semiconductor layer,

wherein the roughness layer is disposed between the third conductive semiconductor layer and the second conductive semiconductor layer,

wherein the third conductive semiconductor layer is disposed between the second electrode and the roughness layer, and

wherein the third conductive semiconductor layer has a rough surface, and

wherein a polarity of the third conductive semiconductor layer is opposite to a polarity of the second conductive semiconductor layer.

2. The light emitting device as claimed in claim 1 , wherein the first conductive semiconductor layer comprises an n-type semiconductor layer and the second conductive semiconductor layer comprises a p-type semiconductor layer.

3. The light emitting device as claimed in claim 1 , comprising at least one of an undoped semiconductor layer, a buffer layer and a substrate under the first conductive semiconductor layer.

4. The light emitting device as claimed in claim 1 , comprising a first electrode electrically connected to the first conductive semiconductor layer.

5. The light emitting device as claimed in claim 1 ,

wherein the third conductive semiconductor layer comprises a plurality of n-type semiconductor layers, and

wherein the plurality of n-type semiconductor layers comprise an n-type clad layer on the roughness layer, and an n-type Al x (Ga 1-x )In 1-y N layer on the n-type clad layer, wherein 0≦x≦1 and 0≦y≦1.

6. The light emitting device as claimed in claim 1 ,

wherein the third conductive semiconductor layer comprises an n-type clad layer on the roughness layer, and a superlattice layer on the n-type clad layer, and

wherein the superlattice layer comprises at least two layers alternatively stacked, the at least two layers selected from the group consisting of AlInGaN, InGaN, GaN, AlInN and AlN.

7. The light emitting device as claimed in claim 5 , wherein the n-type Al x (Ga 1-x )In 1-y N layer of the third conductive semiconductor layer is doped with n-type dopant with an density of 1×10 18 /cm 3 or more.

8. The light emitting device as claimed in claim 1 , wherein the roughness layer comprises an indium dot as the dot shape and comprises a thickness of 1000 Å to 1900 Å.

9. The light emitting device as claimed in claim 1 ,

wherein the third conductive semiconductor layer has a rough surface on the roughness layer, and

wherein the third conductive semiconductor layer is formed of a different material from a material of the roughness layer.

10. The light emitting device as claimed in claim 1 , comprising a transparent electrode layer on the third conductive semiconductor layer.

11. A light emitting device, comprising:

a first conductive semiconductor layer;

an active layer on the first conductive semiconductor;

a second conductive semiconductor layer on the active layer;

a roughness layer including a dot shape on the second conductive semiconductor layer,

a third conductive semiconductor layer on the roughness layer; and

a second electrode on the third conductive semiconductor layer,

wherein the roughness layer is disposed between the third conductive semiconductor layer and the second conductive semiconductor layer, and the third conductive semiconductor layer is disposed between the second electrode and the roughness layer, and

wherein the roughness layer is formed of an indium dot as the dot shape.

12. A light emitting device, comprising:

a first conductive semiconductor layer;

an active layer on the first conductive semiconductor;

a second conductive semiconductor layer on the active layer;

a roughness layer including a dot shape on the second conductive semiconductor layer,

a third conductive semiconductor layer on the roughness layer; and

a second electrode on the third conductive semiconductor layer,

wherein the roughness layer is disposed between the third conductive semiconductor layer and the second conductive semiconductor layer, and the third conductive semiconductor layer is disposed between the second electrode and the roughness layer,

wherein the third conductive semiconductor layer comprises a first cap layer on the roughness layer, and a second cap layer comprising a superlattice layer on the first cap layer, and

wherein the superlattice layer comprises at least two layers alternatively stacked, the at least two layers being selected from the group consisting of AlInGaN, InGaN, GaN, AlInN and AlN.

13. The light emitting device as claimed in claim 12 , wherein the first cap layer comprises a thickness of 1 nm to 10 nm and the second cap layer comprises a thickness of 1 nm to 100 nm.

14. The light emitting device as claimed in claim 12 , comprising a first electrode electrically connected to the first conductive semiconductor layer, and a transparent electrode layer on the third conductive semiconductor layer.

15. The light emitting device as claimed in claim 14 , wherein the transparent electrode layer comprises at least one of the ITO, ZnO, IrOx, RuOx and NiO.

16. A light emitting device, comprising:

a first conductive semiconductor layer;

an active layer on the first conductive semiconductor;

a second conductive semiconductor layer on the active layer;

a roughness layer including a dot shape on the second conductive semiconductor layer,

a third conductive semiconductor layer on the roughness layer; and

a second electrode on the third conductive semiconductor layer,

wherein the roughness layer is disposed between the third conductive semiconductor layer and the second conductive semiconductor layer, and the third conductive semiconductor layer is disposed between the second electrode and the roughness layer, and

wherein the second electrode comprises at least one layer including material selected from the group consisting of Ag, Ni, Al, Rh, Pd, Ir, Ru, Mg, Zn, Pt, Au and Hf, and combinations thereof.

17. The light emitting device as claimed in claim 11 , wherein the third conductive semiconductor layer comprises a plurality of semiconductor layers and an upper surface of the third conductive semiconductor layer is rough.

18. The light emitting device as claimed in claim 17 , wherein at least one layer of the plurality of semiconductor layers of the third conductive semiconductor layer is formed of a semiconductor having a polarity the same as a polarity of the first conductive semiconductor layer.