Light emitting diode and manufacturing method thereof

• US 20060273336A1
• Filed: 09/29/2005
• Published: 12/07/2006
• Est. Priority Date: 06/06/2005
• Status: Active Grant

• Current Assignee: Sumitomo Chemical Company Limited
• Original Assignee: Hitachi Cable Limited (Proterial Ltd.)
• Inventors: Fujikura, Hajime, Nakayama, Satosi
• Granted Patent: US 7,504,667 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: H01L 33/24 of the light emitting region, e.g. non-planar junction
• CPC Class Codes: H01L 33/382 the electrode extending partially in or entirely through the semiconductor body
• CPC Class Codes: H01L 33/42 Transparent materials

Abstract

A technique of ensuring compatibility between the method of improving the light extraction efficiency by roughening the surface of a LED structure, and the method of avoiding the adverse effect of a low-cost electrode pad ((1) forming a current distribution layer by a transparent conductive film made of metal or metal oxide, and (2) forming a flip chip structure). A light emitting diode comprises at least an n-type semiconducting layer, an active layer composed of 30 or less quantum well layers, and a p-type semiconducting layer provided on a substrate, wherein the surface of the semiconductor lamination structure contains a flat portion and a plurality of bores. In this case, the in-plane coverage rate ((the area of the bore opening/surface area)×100) of the plurality of the bores is 10% or more without exceeding 85%; the opening of the bore has a diameter of 100 nm or more without exceeding 4000 nm; the depth of the bore is smaller than the distance between the active layer and the flat portion; and the density of the plurality of the bores expressed in terms of number of bores is 8×10⁵ per/cm² or more without exceeding 1.08×10¹⁰ per/cm².

Claims

1. A light emitting diode of the semiconductor lamination structure comprising at least an n-type semiconducting layer, an active layer composed of 30 or less quantum well layers, and a p-type semiconducting layer provided on a substrate, wherein:

the surface of said semiconductor lamination structure contains a flat portion and a plurality of bores;

the in-plane coverage rate of the plurality of said bores is 10% or more without exceeding 85%;

the opening of said bore has a diameter of 100 nm or more without exceeding 4000 nm;

the depth of said bore is smaller than the distance between said active layer and said flat portion; and

the density of the plurality of said bores expressed in terms of number of bores is 8×

10⁵ per/cm² or more without exceeding 1.08×

10¹⁰ per/cm².

2. The light emitting diode according to claim 1, wherein a transparent conductive film is formed on the surface of said semiconductor lamination structure, an electrode pad is formed on part of the surface of said transparent conductive film, and light is emitted from said transparent conductive film.

3. The light emitting diode according to claim 1, wherein an electrode pad is formed on the surface of said semiconductor lamination structure, and light is emitted from the side of said substrate.

4. The light emitting diode according to claim 2 or 3, wherein the opening of said bore is circular or polygonal.

5. The light emitting diode according to any one of the claims 2 through 4, wherein the depth of said bore is 100 nm or more without exceeding 1000 nm.

6. The light emitting diode according to any one of the claims 2 through 5, wherein said bore is conical or multi-pyramidal.

7. The light emitting diode according to any one of the claims 2 through 6, wherein said n-type semiconducting layer and p-type semiconducting layer are composed of nitride semiconductor.

8. The light emitting diode according to claim 7, wherein said quantum well layer is composed of a well layer containing In_xAl_yGa_zN (where 0≦

y, z≦

1, x+y+z=1), and a barrier layer containing In_aAl_bGa_cN (where 0≦

a, b, c≦

1, a+b+c=1), having a different composition from that of said well layer, and a greater band gap energy than said well layer.

9. The light emitting diode according to claim 8, wherein said well layer is not doped, and said barrier layer is of n-type.

10. The light emitting diode according to any one of claims 7 through 9, wherein the n-type semiconducting layer and/or p-type semiconducting layer is composed of a plurality of layers having different doping densities or compositions.

11. The light emitting diode according to any one of claims 7 through 10, wherein the n-type semiconducting layer contains an undoped GaN layer and an n-type GaN layer.

12. The light emitting diode according to any one of claims 7 through 10, wherein said p-type semiconducting layer includes a p-type AlGaN layer and a p-type GaN layer.

13. The light emitting diode according to any one of claims 7 through 12, wherein said n-type semiconducting layer is formed between said p-type semiconducting layer and substrate.

14. The light emitting diode according to any one of claims 7 through 13, wherein said p-type semiconducting layer is formed between said n-type semiconducting layer and substrate.

15. The light emitting diode according to any one of claims 7 through 14, wherein said substrate is composed of sapphire, SiC, GaN, AlN and ZnO.

16. A light emitting diode manufacturing method comprising:

a step of forming the semiconductor lamination structure by sequentially laminating at least an n-type semiconducting layer, an active layer composed of 30 or less quantum well layers, and a p-type semiconducting layer on a substrate; and

a step of forming a flat portion and a plurality of bores by etching the surface of said semiconductor lamination structure, wherein;

an in-plane coverage rate of said bores is 10% or more without exceeding 85%;

the opening of said bore has a diameter of 100 nm or more without exceeding 4000 nm;

the depth of said bore is smaller than the distance between said active layer and said flat portion; and

the density of the plurality of said bores expressed in terms of number of bores is 8×

10⁵ per/cm² or more without exceeding 1.08×

10¹⁰ per/cm².

17. The light emitting diode manufacturing method according to claim 16, further comprising, after said bore forming step:

a step of forming a transparent conductive film on the surface of said semiconductor lamination structure; and

a step of forming an electrode pad on part of the surface of said transparent conductive film.

18. The light emitting diode manufacturing method according to claim 16, further comprising a step of forming an electrode pad on the surface of said semiconductor lamination structure, after said bore forming step.

19. The light emitting diode manufacturing method according to claim 17 or 18, wherein said etching is provided by wet etching method or electrochemical method using a solution containing at least one of H₂SO₄, H₃PO₄, HCl, KOH, and NaOH.

20. The light emitting diode manufacturing method according to claim 17 or 18, wherein said etching is provided by dry etching method using a gas containing at least one of HCl, Cl₂, SF₆, BCl₃ and CH₄.

31. The light emitting diode manufacturing method according to claim 17, 23 or 26, wherein said transparent conductive film contains at least one of Ni, Au, ITO and ZnO.

32. The light emitting diode manufacturing method according to any one of claims 16 through 31 wherein, after said bore forming step, at least one of the opening of said bore and depth is increased by wet etching method using a solution containing at least one of H₂SO₄, H₃PO₄, HCl, KOH, and NaOH.

33. The light emitting diode manufacturing method according to claim 17, 23, 26 or 31, wherein only said flat portion is covered with a transparent conductive film.

21. A light emitting diode manufacturing method, wherein a semiconductor lamination structure is formed by sequential lamination of:

an n-type semiconducting layer containing an n-type impurity density doped layer, the n-type impurity density being 5×

10¹⁸ per/cm² or more, and the film thickness being 1 μ

m or more;

an active layer composed of 30 or less quantum well layers; and

a p-type semiconducting layer;

said layers being laminated in that order on the substrate;

whereby a flat portion and a plurality of bores are formed on the surface of said semiconductor lamination structure in such a way that;

the in-plane coverage rate of the plurality of said bores is 10% or more without exceeding 85%;

the opening of said bore has a diameter of 100 nm or more without exceeding 4000 nm;

the depth of said bore is smaller than the distance between said active layer and said flat portion; and

the density of the plurality of said bores expressed in terms of number of bores is 8×

10⁵ per/cm² or more without exceeding 1.08×

10¹⁰ per/cm².

23. The light emitting diode manufacturing method according to claim 21 or 22, further comprising, after said bore forming step;

a step of forming a transparent conductive film on the surface of said semiconductor lamination structure; and

a step of forming an electrode pad on part of the surface of said transparent conductive film.

24. The light emitting diode manufacturing method according to claim 21 or 22, further comprising a step of forming an electrode pad on the surface of said semiconductor lamination structure, after said bore forming step.

22. A light emitting diode manufacturing method, comprising a step of sequentially forming:

an n-type semiconducting layer;

an active layer composed of 30 or less quantum well layers; and

a p-type semiconducting layer containing a p-type bore forming layer formed in such a way that;

the substrate temperature Tg is 1,000 degrees Celsius or less;

the film thickness is 100 nm or more without exceeding 1 μ

m; and

the relationship between the substrate temperature Tg and p-type impurity density (unit;

/cm³) can be expressed by p-type impurity density>

4.58×

10¹⁸e^0.00211 Tg;

said layers being formed sequentially in that order;

said light emitting diode manufacturing method further comprising a step of forming a flat portion and a plurality of bores on the surface of said semiconductor lamination structure in such a way that;

the in-plane coverage rate of the plurality of said bores is 10% or more without exceeding 85%;

the opening of said bore has a diameter of 100 nm or more without exceeding 4000 nm;

the depth of said bore is smaller than the distance between said active layer and said flat portion; and

the density of the plurality of said bores expressed in terms of number of bores is 8×

10⁵ per/cm² or more without exceeding 1.08×

10¹⁰ per/cm².

25. A light emitting diode manufacturing method comprising:

a step of forming the semiconductor lamination structure by sequentially laminating at least an n-type semiconducting layer, an active layer composed of 30 or less quantum well layers, and a p-type semiconducting layer on a substrate;

a step of forming a metallic film containing a metal selected from among Ni, W, Al, Ti, Au, Pt, Pd and In and having a thickness of 0.5 nm or more without exceeding 100 nm, on the surface of said semiconductor lamination structure;

a step of forming a flat portion and a plurality of bores on the surface of said semiconductor lamination structure by heat treatment of the semiconductor lamination structure with said metallic film formed thereon, in such a way that;

an in-plane coverage rate of said bores is 10% or more without exceeding 85%;

the opening of said bore has a diameter of 100 nm or more without exceeding 4000 nm;

the depth of said bore is smaller than the distance between said active layer and said flat portion; and

the density of the plurality of said bores expressed in terms of number of bores is 8×

10⁵ per/cm² or more without exceeding 1.08×

10¹⁰ per/cm².

26. The light emitting diode manufacturing method according to claim 25, further comprising, after said bore forming step:

a step of forming a transparent conductive film on the surface of said semiconductor lamination structure; and

a step of forming an electrode pad on part of the surface of said transparent conductive film.

27. The light emitting diode manufacturing method according to claim 25, further comprising a step of forming an electrode pad on the surface of said semiconductor lamination structure, after said bore forming step.

28. The light emitting diode manufacturing method according to claim 26 or 27, wherein the temperature for said heat treatment is 800 or more without exceeding 1300, and the atmosphere for heat treatment comprises any one of a gas consisting of ammonium alone, a mixed gas of ammonium and hydrogen, a mixed gas of ammonium and nitrogen, and a mixed gas of ammonium, hydrogen and nitrogen.

29. The light emitting diode manufacturing method according to any one of claims 26 through 28, wherein, subsequent to said heat treatment, said metallic film is removed by acid solution or alkali solution.

30. The light emitting diode manufacturing method according to any one of claims 26 through 29, wherein said metallic film is a composite metallic film formed by lamination of a plurality of metals.