Nitride Semiconductor Light Emitting Device and Fabrication Method Thereof

• US 20090166649A1
• Filed: 12/05/2005
• Published: 07/02/2009
• Est. Priority Date: 12/23/2004
• Status: Active Grant

• Current Assignee: LG Innotek Company Limited (LG Corporation)
• Original Assignee: LG Innotek Company Limited (LG Corporation)
• Inventors: Lee, Suk Hun
• Granted Patent: US 8,222,654 B2
• Time in Patent Office: Days
• US Class Current: 257/94
• CPC Class Codes: H01L 33/007 comprising nitride compounds
• CPC Class Codes: H01L 33/12 with a stress relaxation structure, e.g. buffer layer

Abstract

The present invention relates to a nitride semiconductor light emitting device including: a substrate having a predetermined pattern formed on a surface thereof by an etch; a protruded portion disposed on a non-etched region of the substrate, and having a first buffer layer and a first nitride semiconductor layer stacked thereon; a second buffer layer formed on the etched region of the substrate; a second nitride semiconductor layer formed on the second buffer layer and the protruded portion; a third nitride semiconductor layer formed on the second nitride semiconductor layer; an active layer formed on the third nitride semiconductor layer to emit light; and a fourth nitride semiconductor layer formed on the active layer. According to the present invention, the optical extraction efficiency of the nitride semiconductor light emitting device can be enhanced.

Claims

1. A nitride semiconductor light emitting device comprising:

a substrate having a predetermined pattern formed on a surface thereof by an etch;

a protruded portion disposed above a non-etched region of the substrate, the protruded portion comprising a first buffer layer and a first nitride semiconductor layer stacked;

a second buffer layer formed above the etched region of the substrate;

a second nitride semiconductor layer formed above the second buffer layer and the protruded portion;

a third nitride semiconductor layer formed above the second nitride semiconductor layer;

an active layer formed above the third nitride semiconductor layer to emit light; and

a fourth nitride semiconductor layer formed above the active layer.

2. The nitride semiconductor light emitting device according to claim 1, wherein the substrate is formed of one selected from the group consisting of sapphire, silicon carbide, silicon, and GaAs.

3. The nitride semiconductor light emitting device according to claim 1, wherein the first buffer layer and/or the second buffer layer have/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_xGa₁₋

xN/GaN, and a stack structure of Al_xIn_yGa<sub>1−

(x+y)</sub>N/In_xGa<sub>1−

x</sub>N/GaN.

4. The nitride semiconductor light emitting device according to claim 1, wherein the first buffer layer and/or the second buffer layer are/is formed of a undoped GaN layer.

5. The nitride semiconductor light emitting device according to claim 1, wherein the first buffer layer and/or the second buffer layer are/is an n-GaN layer doped with one selected from the group consisting of indium, silicon, indium/silicon, and aluminum.

6. The nitride semiconductor light emitting device according to claim 1, wherein the third nitride semiconductor layer is formed of an n-GaN layer simultaneously doped with silicon/indium or silicon/aluminum.

7. The nitride semiconductor light emitting device according to claim 1, wherein the third nitride semiconductor layer is formed, having at least one period of a super lattice structure of AlGaN/GaN(Si) or AlGaN/undoped-GaN/GaN(Si), wherein the period is performed repeatedly.

8. The nitride semiconductor light emitting device according to claim 7, wherein the third nitride semiconductor layer has an overall thickness range of 1˜

2 μ

m.

9. The nitride semiconductor light emitting device according to claim 7, wherein the AlGaN layer is an undoped layer and is formed in a thickness range of 10˜

200 Å

with an Al composition of 0.01˜

0.02 (where 1 corresponds to 100%).

10. The nitride semiconductor light emitting device according to claim 1, further comprising a low mole indium-containing nitride layer formed between the third nitride semiconductor layer and the active layer, wherein the low mole indium-containing nitride layer has an indium content of 1˜

5%.

11. 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, and

wherein a SiNx cluster layer is formed between the well layer and the barrier layer.

12. The nitride semiconductor light emitting device according to claim 1, wherein the fourth nitride semiconductor layer is formed, having at least one period of a super lattice structure of GaN/GaN(Mg), GaN/GaN(Mg)/(Mg⁺⁺) or GaN/(Mg⁺⁺)/GaN(Mg)/(Mg⁺⁺), wherein the period is performed repeatedly.

13. The nitride semiconductor light emitting device according to claim 12, wherein the (Mg⁺⁺) layer is formed by a delta-doping within a time range of 1˜

60 seconds without a supply of Ga.

14. The nitride semiconductor light emitting device according to claim 1, wherein the fourth nitride semiconductor layer is formed, having at least one period of a super lattice structure GaN/AlGaN(Mg), GaN/AlGaN(Mg)/GaN(Mg) or GaN/(Mg⁺⁺)/AlGaN(Mg)/(Mg⁺⁺)/GaN(Mg), wherein the period is performed repeatedly.

15. The nitride semiconductor light emitting device according to claim 14, wherein the (Mg⁺⁺) layer is formed by a delta-doping within a time range of 1˜

60 seconds in an ambient of NH₃/H₂.

16. The nitride semiconductor light emitting device according to claim 1, further comprising a fifth nitride semiconductor layer formed above the fourth nitride semiconductor layer.

17. The nitride semiconductor light emitting device according to claim 16, wherein the fifth nitride semiconductor layer is formed as an n-InGaN layer with an SG (super grading) structure in which indium content is gradually varied, or as an n-InGaN/InGaN super lattice structure layer.

18. The nitride semiconductor light emitting device according to claim 16, further comprising a transparent electrode formed on the fifth nitride semiconductor layer.

19. The nitride semiconductor light emitting device according to claim 18, 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), IrO_x, RuO_x, RuO_x/ITO, Ni/IrO_x/Au, and Ni/IrO_x/Au/ITO.

20. The nitride semiconductor light emitting device according to claim 16, wherein the third and fifth nitride semiconductor layers are formed of an n-type nitride semiconductor layer and the fourth nitride semiconductor layer is formed of a p-type nitride semiconductor layer to provide an n-/p-/n-junction structure.

21. The nitride semiconductor light emitting device according to claim 1, further comprising an insulation layer formed above the protruded portion.

22. The nitride semiconductor light emitting device according to claim 21, wherein the insulation layer is formed of SiO₂.

23. The nitride semiconductor light emitting device according to claim 1, wherein the protruded portion is shaped in a cone.

24. The nitride semiconductor light emitting device according to claim 23, wherein the cone is declined in the form of a gently curved surface.

25. The nitride semiconductor light emitting device according to claim 1, wherein the first buffer layer and the first nitride semiconductor layer are etched while the substrate is etched.

26. A nitride semiconductor light emitting device comprising:

a substrate having a predetermined pattern formed on a surface thereof by an etch;

a protruded portion disposed above a non-etched region of the substrate, the protruded portion comprising a first buffer layer and a first nitride semiconductor layer stacked;

a second buffer layer formed above the etched region of the substrate;

a second nitride semiconductor layer formed above the second buffer layer and the protruded portion;

an active layer formed above the second nitride semiconductor layer to emit light; and

a third nitride semiconductor layer formed above the active layer.

27. A method for fabricating a nitride semiconductor light emitting device, the method comprising:

forming a protruded portion comprising a first buffer layer and a first nitride semiconductor layer above a substrate and forming a predetermined pattern in the substrate by etching a surface of the substrate where the protruded portion is not formed;

forming a second buffer layer above the etched region of the substrate;

forming a second nitride semiconductor layer above the second buffer layer;

forming a third nitride semiconductor layer above the second nitride semiconductor layer;

forming an active layer for emitting light above the third nitride semiconductor layer; and

forming a fourth nitride semiconductor layer above the active layer.

28. The method according to claim 27, further comprising forming a fifth nitride semiconductor layer above the fourth nitride semiconductor layer.

29. The method according to claim 27, wherein the protruded portion is shaped in a cone.

30. The method according to claim 29, wherein the protruded portion has a gently curved part.

31. The method according to claim 27, wherein the second nitride semiconductor layer is formed so as to cover the protruded portion.

32. The method according to claim 27, wherein the forming of the protruded portion and the predetermined pattern in the substrate comprises:

forming the first buffer layer above the substrate;

forming the first nitride semiconductor layer above the first buffer layer;

forming a masking pattern above the first nitride semiconductor layer;

etching the resultant substrate such that a region having the masking pattern thereon forms the protruded portion comprising the first buffer layer and the first nitride semiconductor layer stacked, and a region not having the masking pattern thereon forms the predetermined pattern in the substrate.

33. The method according to claim 32, wherein the substrate and the masking pattern have different etch rates.

34. The method according to claim 32, wherein the masking pattern is formed in the shape of a circle having a two dimension.

35. The method according to claim 32, wherein the masking pattern is formed by a photolithography process.

36. The method according to claim 32, wherein the etching is performed by a dry etch.

37. The method according to claim 32, wherein the region having the masking pattern is etched from an edge thereof.

38. The method according to claim 32, wherein the protruded portion is provided by etching the first buffer layer and the first nitride semiconductor layer.

39. The method according to claim 27, after the forming of the predetermined pattern in the substrate, further comprising:

forming an insulation layer; and

removing the insulation layer on a region where the protruded portion is not formed.

40. The method according to claim 27, wherein the first buffer layer and/or the second buffer layer have/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_xGa_1-xN/GaN, and a stack structure of Al_xIn_yGa₁₋

(x+y)N/In_xGa_1-xN/GaN.

41. The method according to claim 27, wherein the third nitride semiconductor layer is formed of an n-GaN layer simultaneously doped with silicon/indium or silicon/aluminum.

42. The method according to claim 27, wherein the third nitride semiconductor layer is formed in a super lattice structure having at least two periods, wherein a period consists of AlGaN/GaN(Si) or AlGaN/undoped-GaN/GaN(Si).

43. The method according to claim 27, further comprising forming a low mole nitride semiconductor layer having an indium content of 1˜

5% above the third nitride layer.

44. The method according to claim 27, wherein the fourth nitride semiconductor layer is formed in a super lattice structure having at least two periods, wherein a period consists of GaN/GaN(Mg), GaN/GaN(Mg)/(Mg⁺⁺) or GaN/(Mg⁺⁺)/GaN(Mg)/(Mg⁺⁺).

45. The method according to claim 27, wherein the fourth nitride semiconductor layer is formed in a super lattice structure having at least two periods, wherein a period consists of GaN/AlGaN(Mg), GaN/AlGaN(Mg)/GaN(Mg) or GaN/(Mg⁺⁺)/AlGaN(Mg)/(Mg⁺⁺)/GaN(Mg).

46. The method according to claim 27, further comprising forming a fifth nitride semiconductor layer above the fourth nitride semiconductor layer, wherein the fifth nitride semiconductor layer comprises an n-InGaN layer with an SG (super grading) structure in which indium content is gradually varied, or an n-InGaN/InGaN super lattice structure layer.