High-efficiency light-emitting diodes

• US 20030222263A1
• Filed: 06/04/2002
• Published: 12/04/2003
• Est. Priority Date: 06/04/2002
• Status: Abandoned Application

• Current Assignee: Kopin Corporation
• Original Assignee: Kopin Corporation
• Inventors: Choi, Hong K.
• Application Number:
  US10/163,099
• Publication Number:
  US 20030222263A1
• Time in Patent Office: Days
• US Class Current: 257/79
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers

Abstract

Light-emitting diodes (LEDs) have at least one light-emitting surface that is patterned, thereby improving the ratio of internal to external efficiency. In one embodiment, the light-emitting diodes are gallium nitride based group III-V diodes that have a multiple quantum-well active region between an n-doped GaN layer and a p-doped GaN layer. The n-doped GaN layer has a surface that is patterned.

Claims

1. A light-emitting diode, wherein the improvement comprises at least one patterned light-emitting surface.

2. The diode of claim 1, wherein the patterned surface includes an array of essentially hemispherical surface structures.

3. The diode of claim 2, wherein each hemisphere has a diameter at its base in the range of about 0.5 μ

m to about 20 μ

m.

4. The diode of claim 1, wherein the patterned surface includes an array of pyramidal surface structures having an essentially square base.

5. The diode of claim 4, wherein each pyramid has a diagonal at its base in the range of about 0.5 μ

m to about 20 μ

m.

6. The diode of claim 1, wherein the patterned surface includes an array of pyramidal surface structures having an essentially hexagonal base.

7. The diode of claim 6, wherein each hexagonal pyramid has a diagonal at its base in the range of about 0.5 μ

m to about 20 μ

m.

8. The diode of claim 1, wherein the patterned surface that emits light is a semiconductor surface.

9. A light-emitting diode, comprising:

a) a diode structure including;

i) an n-doped semiconductor layer in contact with a p-doped semiconductor layer;

or

ii) an n-doped semiconductor layer having a first surface in contact with a first surface of an active region and a p-doped semiconductor layer having a first surface in contact with a second surface of the active region; and

b) at least one patterned light-emitting surface, whereby light emitted is transmitted through the patterned surface.

10. The diode of claim 9, wherein the patterned light-emitting surface is a surface of the n-doped semiconductor or a surface of the p-doped semiconductor.

11. The diode of claim 10, wherein the patterned light-emitting surface includes an array of essentially hemispherical surface structures.

12. The diode of claim 11, wherein each hemisphere has a diameter at its base in the range of about 0.5 μ

m to about 20 μ

m.

13. The diode of claim 10, wherein the patterned light-emitting surface includes an array of pyramidal surface structures having an essentially square base.

14. The diode of claim 13, wherein each pyramid has a diagonal at its base in the range of about 0.5 μ

m to about 20 μ

m.

15. The diode of claim 10, wherein the patterned surface includes an array of pyramidal surface structures having an essentially hexagonal base.

16. The diode of claim 15, wherein each hexagonal pyramid has a diagonal at its base in the range of about 0.5 μ

m to about 20 μ

m.

17. The diode of claim 9, wherein the p-doped semiconductor layer and the n-doped semiconductor layer are GaN and the active region has multiple quantum-well layers comprising In_xGa₁₋

xN, wherein 0<

×

≦

1, and multiple barrier layers comprising In_yGa<sub>1−

y</sub>N, wherein 0≦

y≦

1 and y<

x.

18. The diode of claim 9, further comprising a transparent substrate having a first surface and a second surface, wherein the first surface is in contact with a surface of the n-doped semiconductor layer or a surface of the p-doped semiconductor layer, and wherein the second surface of the substrate is the patterned light-emitting surface.

19. The diode of claim 18, wherein the second substrate surface includes an array of essentially hemispherical surface structures.

20. The diode of claim 19, wherein each hemisphere has a diameter at its base in the range of about 0.5 μ

m to about 20 μ

m.

21. The diode of claim 18, wherein the second substrate surface includes an array of pyramidal surface structures having an essentially square base.

22. The diode of claim 21, wherein each pyramid has a diagonal at its base in the range of about 0.5 μ

m to about 20 μ

m.

23. The diode of claim 18, wherein the patterned surface includes an array of pyramidal surface structures having an essentially hexagonal base.

24. The diode of claim 23, wherein each hexagonal pyramid has a diagonal at its base in the range of about 0.5 μ

m to about 20 μ

m.

25. The diode of claim 18, wherein the substrate includes GaAs and the n-doped and the p-doped semiconductor layers include InGaAs.

26. The diode of claim 18, wherein the substrate includes InP and the n-doped and the p-doped semiconductor layers include InGaAsP.

27. The diode of claim 18, wherein the substrate includes GaN and the n-doped and the p-doped semiconductor layers include InGaN.

28. A light-emitting diode, comprising:

a) an n-doped GaN layer having a first and a second surface, wherein the first surface emits light and is patterned;

b) a multiple quantum-well active region having a first surface in contact with the second surface of the n-doped GaN layer, wherein the multiple quantum-well active region comprises multiple In_xGa<sub>1−

x</sub>N well layers, wherein 0<

×

≦

1, and multiple In_yGa<sub>1−

y</sub>N barrier layers, wherein 0≦

y≦

1 and y<

x;

c) a p-doped GaN layer having a first and a second surface, wherein the first surface of the p-doped GaN layer is in contact with a second surface of the active region and the second surface is in contact with an ohmic contact layer and a light reflecting layer; and

d) a silicon, germanium, gallium arsenide or metallic substrate bound to the ohmic contact layer with an electrically-conducting bonding layer.

29. The diode of claim 28, wherein a reflective layer is between the ohmic contact layer and the bonding layer.