Nitride semiconductor light emitting device and fabrication method thereof

1. A nitride semiconductor light emitting device comprising:

a substrate;

a first buffer layer on the substrate;

an indium-containing second buffer layer on the first buffer layer;

an indium-containing third buffer layer on the second buffer layer, wherein the third buffer layer has substantially the same indium content as the second buffer layer;

an indium-doped nitride semiconductor layer on the third buffer layer;

a first nitride semiconductor layer on the indium-doped nitride semiconductor layer;

an active layer on the first nitride semiconductor layer; and

a second nitride semiconductor layer on the active layer.

2. The nitride semiconductor light emitting device according to claim 1 , wherein the first buffer layer has a structure selected from the group consisting of a stack structure of AlInN/GaN, a super lattice structure of InGaN/GaN, a stack structure of In x Ga 1-x N/GaN, a stack structure of Al x In y Ga 1 -(x+y)N/In x Ga 1-x N/GaN, and a stack structure of AlInN/AlN.

3. The nitride semiconductor light emitting device according to claim 1 , wherein the second buffer layer has a single crystal.

4. The nitride semiconductor light emitting device according to claim 1 , wherein the first nitride semiconductor layer is an n-GaN layer doped with silicon/indium or silicon/aluminum.

5. The nitride semiconductor light emitting device according to claim 1 , wherein the first nitride semiconductor layer is a delta-doped n-GaN layer.

6. The nitride semiconductor light emitting device according to claim 1 , further comprising a low mole nitride semiconductor layer formed between the first nitride semiconductor layer and the active layer, wherein the low mole nitride semiconductor layer has an indium content of 1-5%.

7. The nitride semiconductor light emitting device according to claim 1 , wherein the active layer is formed as a single quantum well layer or a multi quantum well layer comprising a well layer and a barrier layer, wherein a SiNx cluster layer is formed between the well layer and the barrier layer.

8. The nitride semiconductor light emitting device according to claim 1 , wherein the indium content contained in the second buffer layer is less than 10%.

9. The nitride semiconductor light emitting device according to claim 1 , wherein the third buffer layer is a single crystal InGaN layer which substantially has the same indium content as the second buffer layer.

10. The nitride semiconductor light emitting device according to claim 1 , wherein the second nitride semiconductor layer is formed by a delta doping in which a concentration of a doped material is periodically varied, and is a p-GaN layer which is delta-doped with magnesium and/or aluminum.

11. The nitride semiconductor light emitting device according to claim 1 , wherein the first nitride semiconductor layer is an n-type first electrode contact layer and the second nitride semiconductor layer is a p-type second electrode contact layer.

12. A nitride semiconductor light emitting device comprising:

a substrate;

a first buffer layer on the substrate;

an indium-containing second buffer layer on the first buffer layer;

an indium-containing third buffer layer on the second buffer layer;

an indium-doped nitride semiconductor layer on the third buffer layer;

a first nitride semiconductor layer on the indium-doped nitride semiconductor layer;

an active layer on the first nitride semiconductor layer;

a second nitride semiconductor layer on the active layer; and

a third nitride semiconductor layer the second nitride semiconductor layer.

13. The nitride semiconductor light emitting device according to claim 12 , wherein the third nitride semiconductor layer is formed of an n-InGaN layer in a super grading structure in which indium content is varied.

14. The nitride semiconductor light emitting device according to claim 12 , further comprising a transparent electrode formed above the third nitride semiconductor layer.

15. The nitride semiconductor light emitting device according to claim 14 , wherein the transparent electrode is formed of one selected from the group consisting of ITO, IZO(In-ZnO), GZO(Ga—ZnO), AZO(Al—ZnO), AGZO(Al—Ga ZnO), IGZO(In—Ga ZnO), IrOx, RuO x , RuO x /ITO, Ni/IrO x /Au, and Ni/IrO x /Au/ITO.

16. The nitride semiconductor light emitting device according to claim 12 , wherein the second buffer layer has a higher growth temperature than that of the first buffer layer.

17. The nitride semiconductor light emitting device according to claim 12 , wherein the third buffer layer has a higher growth temperature than that of the second buffer layer, the growth temperature of the third buffer layer being increased.

18. The nitride semiconductor light emitting device according to claim 12 , wherein the first nitride semiconductor layer is an n-type first electrode contact layer and the third nitride semiconductor layer is an n-type second electrode contact layer.

19. A nitride semiconductor light emitting device comprising:

a substrate;

a first buffer layer on the substrate;

a second buffer layer on the first buffer layer, wherein the first buffer layer and the second buffer layer each has substantially the same tensile strain as the substrate;

a third buffer layer comprising indium on the second buffer layer;

a first electrode contact layer on the third buffer layer;

an active layer on the first electrode contact layer; and

a second electrode contact layer on the active layer.

20. The nitride semiconductor light emitting device according to claim 19 , wherein the first buffer layer has a recrystallized structure.

21. The nitride semiconductor light emitting device according to claim 19 , wherein the third buffer layer has substantially the same indium content as the second buffer layer.