LIGHT EMITTING DIODE AND METHOD OF FABRICATING THEREOF

• US 20060273333A1
• Filed: 08/18/2005
• Published: 12/07/2006
• Est. Priority Date: 06/03/2005
• Status: Abandoned Application

• Current Assignee: Formosa Epitaxy Incorporated (Epistar Corporation)
• Original Assignee: Formosa Epitaxy Incorporated (Epistar Corporation)
• Inventors: Chien, Fen-Ren, Wu, Liang-Wen, Chen, Ming-Sheng
• Application Number:
  US11/161,825
• Publication Number:
  US 20060273333A1
• Time in Patent Office: Days
• US Class Current: 257/94
• 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 33/40 Materials therefor

Abstract

A light emitting diode (LED) is made of a substrate and an epitaxial structure. A surface of the epitaxial structure has many mass transferred patterns. The mass transferred patterns are formed by a mass transfer method to deform an original rough surface of the epitaxial structure. The surface topography of the mass transferred patterns is smoother and more gradual than that of the original rough surface of the epitaxial structure, and thus the light extraction efficiency of the LED is improved. In addition, the issue of instrument detection errors related to device positioning due to the roughness or the patterns of the LED surface can be reduced.

Claims

1. A light emitting diode, comprising a substrate and an epitaxial structure disposed on the substrate, wherein comprising:

a surface of the epitaxial structure having a plurality of mass transferred patterns, forming the mass transferred patterns by means of a mass transfer method undergoing deformations of the original rough surface of the epitaxial structure, wherein a surface topography of the mass transferred pattern is smoother and more gradual than a surface topography of the original surface of the epitaxial structure.

2. The light emitting diode according to claim 1, wherein the distance between each of the mass transferred patterns is between 0.1 μ

m and 5 μ

m.

3. The light emitting diode according to claim 1, wherein the surface of each of the mass transferred pattern is the same as the surface of a microlens.

4. The light emitting diode according to claim 1, wherein the substrate comprises C-Plane sapphire, R-Plane sapphire, A-Plane sapphire, SiC, Si, ZnO, GaAs, spinel, or single crystalline compounds with lattice constant same as semiconductor nitrides.

5. The light emitting diode according to claim 1, wherein the substrate comprises a surface patterned substrate.

6. The light emitting diode according to claim 1, further comprising a regrowth mask disposed in the epitaxial structure.

7. The light emitting diode according to claim 1, wherein the epitaxial structure comprising:

a buffer layer, disposed on the substrate;

a first contact layer, disposed on the buffer layer;

an active layer, disposed on the first contact layer;

a clad layer, disposed on the active layer; and

a second contact layer, disposed on the clad layer.

8. The light emitting diode according to claim 7, wherein:

material of the buffer layer comprising Al_aGa_bIn_1-a-bN, wherein 0≦

a,b<

1, a+b≦

1;

material of the first contact layer comprising gallium nitride series material;

material of the active layer comprising indium gallium nitride;

material of the clad layer comprising gallium nitride series material; and

material of the second contact layer comprising gallium nitride series material.

9. The light emitting diode according to claim 7, further comprising a first electrode, disposed on the first contact layer;

a second electrode, disposed on the second contact layer and the surfaces of the mass transferred patterns; and

a transparent conductive layer, disposed on the second contact layer and a plurality of the mass transferred patterns, wherein the transparent conductive layer and the second electrode do not mutually overlap.

10. The light emitting diode according to claim 9, wherein the first electrode is a negative electrode, wherein the first electrode is made of Al, Pt, Pd, Co, Mo, Be, Au, Ti, Cr, Sn, Ta, TiN, TiWNx or WSiy fabricated in the form of metal or alloy in single layer or multiple layers.

11. The light emitting diode according to claim 9, wherein the second electrode is a positive electrode, wherein the second electrode is made of Ni, Pt, Pd, Co, Be, Au, Ti, Cr, Sn, Ta, TiN, TiWNx , or WSiy fabricated in the form of metal or alloy in single layer or multiple layers.

12. The light emitting diode according to claim 9, wherein the transparent conductive layer comprising a metal layer or a transparent conductive oxide layer.

13. The light emitting diode according to claim 12, wherein the metal layer is made of Ni, Pt, Pd, Co, Be, Au, Ti, Cr, Sn or Ta fabricated in the form of metal or alloy in single layer or multiple layers.

14. The light emitting diode according to claim 12, wherein the transparent conductive oxide (TCO) layer is made from at least one material of ITO, CTO, ZnO:

Al, ZnGa₂O₄, SnO₂;

Sb, Ga₂O₃;

Sn, AglnO₂;

Sn, In₂O₃;

Zn, CuAlO₂, LaCuOS, NiO, CuGaO₂, or SrCu₂O₂ fabricated in the form of single layer or multiple layers.

15. The light emitting diode according to claim 7, wherein the first contact layer comprising a n-type contact layer and the second contact layer comprising a p-type contact layer.

16. The light emitting diode according to claim 7, wherein the clad layer comprises a p-type clad layer.

17. The light emitting diode according to claim 7, further comprises a regrowth mask disposed between the substrate and the active layer.

18. A fabrication method for a light emitting diode, comprising providing an epitaxial structure on a substrate, wherein a surface of the epitaxial structure has a plurality of first patterns;

and

undergoing deformation to the first pattern of the surface and forming a plurality of second patterns using a mass transfer method, wherein a surface topography of each of the second pattern is smoother and more gradual than a surface topography of each of the first pattern.

19. The fabrication method for the light emitting diode according to claim 18, wherein the mass transfer phenomenon occurs at temperature between 800°

C. and 1400°

C. in the mass transfer method.

20. The fabrication method for the light emitting diode according to claim 18, wherein the distance between each of the second patterns is between 0.1 μ

m and 5 μ

m.

21. The fabrication method for the light emitting diode according to claim 18, wherein the height of each of the first pattern is between 500 angstrom and 10000 angstrom.

22. The fabrication method for the light emitting diode according to claim 18, wherein the width of each of the first pattern is between 0.1 μ

m and 5 μ

m.

23. The fabrication method for the light emitting diode according to claim 18, wherein the procedure for providing the epitaxial structure on the substrate comprising:

forming a buffer layer, a first contact layer, an active layer, a clad layer, and a second contact layer sequentially above the substrate; and

forming the plurality of first patterns using fabrication method at the surface of the second contact layer.

24. The fabrication method for the light emitting diode according to claim 23, further comprising:

forming a first electrode on the first contact layer; and

forming a second electrode and a transparent conductive layer on the second contact layer and a plurality of second patterns, wherein the transparent conductive layer and the second electrode do not mutually overlap.

25. The fabrication method for the light emitting diode according to claim 18, wherein the procedure for providing the epitaxial structure on the substrate comprising:

providing a surface patterned substrate as the substrate, wherein the surface of the surface patterned substrate having a plurality of surface patterns; and

forming a buffer layer, a first contact layer, an active layer, a clad layer, and a second contact layer sequentially above the substrate.

26. The fabrication method for the light emitting diode according to claim 25, further comprising:

forming a first electrode on the first contact layer; and

forming a second electrode and a transparent conductive layer on the second contact layer and a plurality of second patterns, wherein the transparent conductive layer and the second electrode do not mutually overlap.

27. The fabrication method for the light emitting diode according to claim 18, wherein the procedure for providing the epitaxial structure on the substrate comprising:

forming a buffer layer, a first contact layer, an active layer, and a clad layer sequentially above the substrate; and

forming a second contact layer on the clad layer , and forming a plurality of first patterns on the second contact layer using changes in epitaxial conditions.

28. The fabrication method for the light emitting diode according to claim 27, further comprising:

forming a first electrode on the first contact layer; and

forming a second electrode and a transparent conductive layer on the second contact layer and a plurality of second patterns, wherein the transparent conductive layer and the second electrode do not mutually overlap.

29. The fabrication method for the light emitting diode according to claim 18, wherein the procedure for providing the epitaxial structure on the substrate comprising:

forming a regrowth mask in the epitaxial structure, wherein the pattern of the regrowth mask and the position of a plurality of first patterns are mirror images of one another.

30. The fabrication method for the light emitting diode according to claim 29, wherein the procedure for providing the epitaxial structure on the substrate comprising:

forming a buffer layer, a first contact layer, an active layer, a clad layer, and a second contact layer sequentially above the substrate, wherein the regrowth mask is formed on the substrate, in the buffer layer, or in the first contact layer.

31. The fabrication method for the light emitting diode according to claim 30, further comprising:

forming a first electrode on the first contact layer; and

forming a second electrode and a transparent conductive layer on the second contact layer and a plurality of second patterns, wherein the transparent conductive layer and the second electrode do not mutually overlap.

32. The fabrication method for the light emitting diode according to claim 29, wherein the procedure for providing the epitaxial structure on the substrate comprising:

forming a buffer layer, a first contact layer, an active layer, a clad layer, and a second contact layer sequentially above the substrate, wherein;

forming the regrowth mask between the substrate and the active layer; and

forming the cystal of the light emitting diode using epitaxial method of epitaxial lateral over growth (ELOG) or PENDEO.

33. The fabrication method for the light emitting diode according to claim 32, further comprising:

forming a first electrode on the first contact layer; and

forming a second electrode and a transparent conductive layer on the second contact layer and a plurality of second pattern, wherein the transparent conductive layer and the second electrode do not mutually overlap.