Light emitting diode having surface containing flat portion and plurality of bores

• US 7,504,667 B2
• Filed: 09/29/2005
• Issued: 03/17/2009
• Est. Priority Date: 06/06/2005
• Status: Expired due to Fees

• Current Assignee: Sumitomo Chemical Company Limited
• Original Assignee: Hitachi Cable Limited (Proterial Ltd.)
• Inventors: Nakayama, Satosi, Fujikura, Hajime
• Primary Examiner(s): Phung; Anh
• Assistant Examiner(s): BERNSTEIN, ALLISON
• Application Number:
  US11/237,796
• Publication Number:
  US 20060273336A1
• Time in Patent Office: 1,265 Days
• Field of Search: 257/98, 257/94, 257/95, 257/E33.006, 257/E33.008, 257/E33.074, 362/800
• 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 has 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,

a p-type semiconducting layer provided on a substrate, wherein the surface of said semiconductor lamination structure contains a flat portion and bores;

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

10⁵ per/cm² or more without exceeding 1.08×

10¹⁰ per/cm², and

a transparent conductive film covering a plurality of said bores.

2. The light emitting diode according to claim 1, wherein said bore is conical.

3. The light emitting diode according to claim 1, wherein said n-type semiconducting layer and p-type semiconducting layer are composed of nitride semiconductor.

4. The light emitting diode according to claim 3, wherein said quantum well layer is composed of a well layer containing In_xAl_yGa_zN (where 0≦

x, 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.

5. The light emitting diode according to claim 4, wherein said well layer is not doped, and said barrier layer is of n-type.

6. The light emitting diode according to claim 3, 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.

7. The light emitting diode according to claim 6, wherein the n-type semiconducting layer contains an undoped GaN layer and an n-type GaN layer.

8. The light emitting diode according to claim 6, wherein said p-type semiconducting layer includes a p-type AIGaN layer and a p-type GaN layer.

9. The light emitting diode according to claim 3, wherein said n-type semiconducting layer is formed between said p-type semiconducting layer and substrate.

10. The light emitting diode according to claim 3, wherein said p-type semiconducting layer is formed between said n-type semiconducting layer and substrate.

11. The light emitting diode according to claim 1, wherein said active layer is composed of a plurality of quantum well layers.

12. The light emitting diode according to claim 1, wherein said flat portion is provided on a surface of said n-type semiconducting layer, and said bores are provided on a surface of said p-type semiconducting layer.

13. The light emitting diode according to claim 12, wherein a first electrode pad is provided on said transparent conductive film, and a second electrode pad is provided on said flat portion of said n-type semiconducting layer.

14. The light emitting diode according to claim 1, wherein all of said bores are formed in an outermost surface semiconductor layer of said semiconductor lamination structure.

15. A light emitting diode having a semiconductor lamination structure, comprising:

a substrate;

an n-type semiconducting layer provided on the substrate, wherein a surface of the n-type semiconducting layer opposite a surface adjacent the substrate contains a flat portion and bores;

an active layer composed of 30 or less quantum well layers provided on at least a portion of the n-type semiconducting layer containing the bores, wherein a surface of the active layer opposite a surface adjacent the n-type semiconducting layer contains bores corresponding to the bores in the surface of the n-type semiconducting layer;

a p-type semiconducting layer provided on the active layer, wherein a surface of the p-type semiconducting layer opposite a surface adjacent the active layer contains bores corresponding to the bores in the surface of the active layer and the n-type semiconducting layer, and wherein the bores in the surface of the p-type semiconducting layer have an in-plane coverage rate of 10% or more without exceeding 85%, the opening of each bore has a diameter of 100 nm or more without exceeding 4000 nm, the depth of each bore is 100 nm or more and smaller than the distance between the active layer and the flat portion, and the density of the bores expressed in terms of number of bores is 8×

10⁵ per/cm² or more without exceeding 1.08×

10¹⁰ per/cm²; and

a transparent conductive film covering a plurality of the bores.

16. The light emitting diode according to claim 15, further comprising a buffer layer provided between the substrate and the n-type semiconducting layer.

17. The light emitting diode according to claim 15, wherein the depth of each bore is 100 nm or more without exceeding 1000 nm.

18. The light emitting diode according to claim 15, wherein each bore is conical.

19. The light emitting diode according to claim 15, wherein each bore is multi-pyramidal.

20. The light emitting diode according to claim 15, wherein the n-type semiconducting layer and the p-type semiconducting layer are composed of nitride semiconductor.

21. The light emitting diode according to claim 20, wherein each of the quantum well layers is composed of a well layer containing In_xAl_yGa_zN (where 0≦

x, 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 the well layer, and a greater band gap energy than the well layer.

22. The light emitting diode according to claim 21, wherein the well layer is not doped, and the barrier layer is of n-type.

23. The light emitting diode according to claim 20, wherein the n-type semiconducting layer and/or the p-type semiconducting layer is composed of a plurality of layers having different doping densities or compositions.

24. The light emitting diode according to claim 23, wherein the n-type semiconducting layer contains an undoped GaN layer and an n-type GaN layer.

25. The light emitting diode according to claim 23, wherein said p-type semiconducting layer includes a p-type AIGaN layer and a p-type GaN layer.

26. The light emitting diode according to claim 15, wherein the active layer is composed of a plurality of quantum well layers.

27. The light emitting diode according to claim 15, further comprising a first electrode pad provided on the transparent conductive film, and a second electrode pad provided on the flat portion of the n-type semiconducting layer.