Selective placement of quantum wells in flipchip light emitting diodes for improved light extraction

• US 20020190260A1
• Filed: 05/29/2002
• Published: 12/19/2002
• Est. Priority Date: 12/22/1999
• Status: Active Grant

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Lumileds Lighting US LLC (Apollo Global Management, Inc.)
• Inventors: Krames, Michael R., Shen, Yu-Chen, Ludowise, Michael J.
• Granted Patent: US 6,903,376 B2
• Time in Patent Office: Days
• US Class Current: 257/81
• CPC Class Codes: G09G 2360/148 the light being detected by light detection means within each pixel
• CPC Class Codes: H01L 2224/05001 Internal layers
• CPC Class Codes: H01L 2224/05023 the whole internal layer protruding from the surface
• CPC Class Codes: H01L 2224/051 with a principal constituent of the material being a metal or a metalloid, e.g. boron [B], silicon [Si], germanium [Ge], arsenic [As], antimony [Sb], tellurium [Te] and polonium [Po], and alloys thereof
• CPC Class Codes: H01L 2224/05572 the external layer extending out of an opening
• CPC Class Codes: H01L 2224/056 with a principal constituent of the material being a metal or a metalloid, e.g. boron [B], silicon [Si], germanium [Ge], arsenic [As], antimony [Sb], tellurium [Te] and polonium [Po], and alloys thereof
• CPC Class Codes: H01L 2224/0603 Bonding areas having different sizes, e.g. different heights or widths
• CPC Class Codes: H01L 2224/06051 Bonding areas having different shapes
• CPC Class Codes: H01L 2224/16 of an individual bump connector
• CPC Class Codes: H01L 24/05 of an individual bonding area
• CPC Class Codes: H01L 27/156 two-dimensional arrays
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/01019 Potassium [K]
• CPC Class Codes: H01L 2924/01025 Manganese [Mn]
• CPC Class Codes: H01L 2924/01046 Palladium [Pd]
• CPC Class Codes: H01L 2924/01068 Erbium [Er]
• CPC Class Codes: H01L 2924/01078 Platinum [Pt]
• CPC Class Codes: H01L 2924/01079 Gold [Au]
• CPC Class Codes: H01L 2924/01322 Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
• CPC Class Codes: H01L 2924/12041 LED
• CPC Class Codes: H01L 33/025 : Physical imperfections, e.g. particular concentration or distribution of impurities
• CPC Class Codes: H01L 33/08 : with a plurality of light emitting regions, e.g. laterally discontinuous light emitting layer or photoluminescent region integrated within the semiconductor body H01L27/15 takes precedence
• CPC Class Codes: H01L 33/20 : with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/38 : with a particular shape
• CPC Class Codes: H01L 33/405 : Reflective materials
• CPC Class Codes: H01L 33/52 : Encapsulations
• CPC Class Codes: H01L 33/56 : Materials, e.g. epoxy or silicone resin
• CPC Class Codes: H01L 33/62 : Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls
• CPC Class Codes: H01L 33/641 : characterized by the materials
• CPC Class Codes: H01L 33/647 : the elements conducting electric current to or from the semiconductor body

Abstract

In accordance with embodiments of the invention, a light emitting device includes a light emitting region and a reflective contact separated from the light emitting region by one or more layers. In a first embodiment, the separation between the light emitting region and the reflective contact is between about 0.5λ_n and about 0.9λ_n, where λ_n is the wavelength of radiation emitted from the light emitting region in an area of the device separating the light emitting region and the reflective contact. In a second embodiment, the separation between the light emitting region and the reflective contact is between about λ_n and about 1.4λ_n. The light emitting region may be, for example, III-nitride, III-phosphide, or any other suitable material.

Claims

1. A light emitting diode comprising:

a light emitting region capable of emitting radiation; and

a reflector reflective of the radiation and separated from the light emitting region by a separation, wherein the separation is such that interferences between direct and reflected beams of the emitted radiation cause radiation to concentrate in a top escape cone of the light emitting device.

2. The light emitting diode of claim 1 wherein the radiation is concentrated in a top escape cone of the light emitting device, but not on a central perpendicular axis of the light emitting region.

3. A light emitting diode comprising:

a light emitting region capable of emitting radiation; and

a reflector reflective of the radiation;

wherein the reflector is separated from the light emitting region by a separation ranging between about 0.5λ

_and about 0.9λ

_n, wherein λ

_n is the wavelength of the radiation within a region separating the light emitting region from the reflector.

4. The light emitting diode of claim 3 wherein the reflector comprises silver and nickel.

5. The light emitting diode of claim 4 wherein the light emitting region comprises Al_xIn_yGa_zN, wherein 0≦

x≦

1, 0≦

y≦

1, 0≦

z≦

1, and x+y+z=1.

6. The light emitting diode of claim 4 wherein the separation is between about 0.6λ

_n and about 0.75λ

_n.

7. The light emitting diode of claim 4 wherein:

the radiation has a wavelength of 450 nm in a vacuum; and

the separation is between about 93.8 nm and about 150.0 nm.

8. The light emitting diode of claim 4 wherein:

the radiation has a wavelength of 505 nm in a vacuum; and

the separation is between about 111.5 mn and about 174.6 nm.

9. The light emitting diode of claim 4 wherein:

the radiation has a wavelength of 530 nm in a vacuum; and

the separation is between about 121.5 nm and about 187.7 nm.

10. The light emitting diode of claim 3 wherein the reflector comprises silver.

11. The light emitting diode of claim 10 wherein the light emitting region comprises Al_xIn_yGa_xN, wherein 0≦

x≦

1, 0≦

y≦

1, 0≦

z≦

1, and x+y+z=1.

12. The light emitting diode of claim 10 wherein the separation is between about 0.65λ

_n and about 0.754λ

_n.

13. The light emitting diode of claim 3 wherein the reflector comprises one of gold and gold alloy.

14. The light emitting diode of claim 13 wherein the light emitting region comprises Al_xIn_yGa_zP, wherein 0≦

x≦

1, 0≦

y≦

1, 0≦

z≦

1, and x+y+z=1.

15. The light emitting diode of claim 13 wherein the separation is between about 0.6λ

_n and about 0.75λ

_n.

16. The light emitting diode of claim 3 wherein the reflector has a reflectance greater than 80%.

17. The light emitting diode of claim 3 wherein the reflector has a reflectance greater than 90%.

18. The light emitting diode of claim 3 wherein the light emitting region comprises a plurality of quantum wells.

19. The light emitting diode of claim 18 wherein the separation is from a center of brightness of the plurality of quantum wells to the reflector.

20. The light emitting diode of claim 3 further comprising:

a region of first conductivity type near a first side of the light emitting region;

a region of second conductivity type near a second side of the light emitting region;

a first contact electrically connected to the region of first conductivity type;

a second contact electrically connected to the region of second conductivity type; and

a submount electrically connected to the first and second contacts.

21. The light emitting diode of claim 20 further comprising a lens overlying the light emitting region.

22. A light emitting diode comprising:

a light emitting region capable of emitting radiation; and

a reflector reflective of the radiation;

wherein the reflector is separated from the light emitting region by a separation ranging between about λ

_n and about 1.4λ

_n, wherein λ

_n is the wavelength of the radiation within a region separating the light emitting region from the reflector.

23. The light emitting diode of claim 22 wherein:

the reflector comprises silver and nickel;

the light emitting region comprises Al_xIn_yGa_zN, wherein 0≦

x≦

1, 0≦

y≦

1, 0≦

z≦

1, and x+y+z=1; and

the separation is between about 1.05λ

_n and about 1.4λ

_n.

24. The light emitting diode of claim 23 wherein the separation is between about 1.15λ

_n and about 1.34λ

_n.

25. The light emitting diode of claim 23 wherein:

the radiation has a wavelength of 450 nm in a vacuum; and

the separation is between about 196.9 nm and about 253.1 nm.

26. The light emitting diode of claim 23 wherein:

the radiation has a wavelength of 505 nm in a vacuum; and

the separation is between about 227.3 nm and about 290.4 nm.

27. The light emitting diode of claim 23 wherein:

the radiation has a wavelength of 530 nm in a vacuum; and

the separation is between about 242.9 nm and about 309.2 nm.

28. The light emitting diode of claim 22 wherein:

the reflector comprises silver;

the light emitting region comprises Al_xIn_yGa_zN, wherein 0≦

x≦

1, 0≦

y≦

1, 0≦

z≦

1, and x+y+z=1; and

the separation is between about 1.15λ

_n and about 1.38λ

_n.

29. The light emitting diode of claim 22 wherein:

the reflector comprises one of gold and gold alloy;

the light emitting region comprises Al_xIn_yGa_zP, wherein 0≦

x≦

1, 0≦

y≦

1, 0≦

z≦

1, and x+y+z=1; and

the separation is between about 1.1λ

_n and about 1.25λ

_n.

30. The light emitting diode of claim 22 wherein the light emitting region comprises a plurality of quantum wells.

31. The light emitting diode of claim 30 wherein the separation is from a center of brightness of the plurality of quantum wells to the reflector.

32. A light emitting diode comprising:

a light emitting region capable of emitting radiation; and

a reflector reflective of the radiation;

wherein the reflector is separated from the light emitting region by a separation ranging between about 1.55λ

_n and about 1.95λ

_n, wherein λ

_n is the wavelength of the radiation within a region separating the light emitting region from the reflector.

33. The light emitting diode of claim 32 wherein:

the reflector comprises silver and nickel;

the light emitting region comprises Al_xIn_yGa_zN, wherein 0≦

x≦

1, 0≦

y≦

1, 0≦

z≦

1, and x+y+z=1; and

the separation is between about 1.65λ

_n and about 1.8λ

_n.

34. The light emitting diode of claim 32 wherein:

the reflector comprises silver;

the light emitting region comprises Al_xIn_yGa_zN, wherein 0≦

x≦

1, 0≦

y≦

1, 0≦

z≦

1, and x+y+z=1; and

the separation is between about 1.73λ

_n and about 1.85λ

_n.

35. The light emitting diode of claim 32 wherein:

the reflector comprises one of gold and gold alloy;

the light emitting region comprises Al_xIn_yGa_zP, wherein 0≦

x≦

1, 0≦

y≦

1, 0≦

z≦

1, and x+y+z=1; and

the separation is between about 1.6λ

_n and about 1.8λ

_n.

37. The method of claim 36 further comprising fabricating a light emitting diode having an active region separated from a reflector by the separation distance.

39. The method of claim 38 wherein:

the reflector comprises silver and nickel;

the light emitting region comprises Al_xIn_yGa_zN, wherein 0≦

x≦

1, 0≦

y≦

1, 0≦

z≦

1, and x+y+z=1; and

the separation is between about 0.6λ

_n and about 0.75λ

_n.

40. The method of claim 38 wherein:

the reflector comprises silver;

the light emitting region comprises Al_xIn_yGa_zN, wherein 0≦

x≦

1, 0≦

y≦

1, 0≦

z≦

1, and x+y+z=1; and

the separation is between about 0.65λ

_n and about 0.75λ

_n.

41. The method of claim 38 wherein:

the reflector comprises one of gold and gold alloy;

the light emitting region comprises Al_xIn_yGa_zP, wherein 0≦

x≦

1, 0≦

y≦

1, 0≦

z≦

1, and x+y+z=1; and

the separation is between about 0.6λ

_n and about 0.7λ

_n.

42. A far-field pattern of light intensity emitted from a light emitting diode as an article of manufacture, the pattern produced according to the method of claim 38.

43. The method of claim 38 wherein the light emitting region comprises multiple quantum wells and the separation is from a center of brightness of the multiple quantum wells to the reflector.

44. A far-field pattern of light intensity emitted from a light emitting diode as an article of manufacture, the pattern produced according to the method of claim 43.

46. The method of claim 45 wherein:

the reflector comprises silver and nickel;

the light emitting region comprises Al_xIn_yGa_zN, wherein 0≦

x≦

1, 0≦

y≦

1, 0≦

z≦

1, and x+y+z=1; and

the separation is between about 1.15λ

_n and about 1.3λ

_n.

47. The method of claim 45 wherein:

the reflector comprises silver;

the light emitting region comprises Al_xIn_yGa_zN, wherein 0≦

x≦

1, 0≦

y≦

1, 0≦

z≦

1, and x+y+z=1; and

the separation is between about 1.2λ

_n and about 1.3λ

_n.

48. The method of claim 45 wherein:

the reflector comprises one of gold and gold alloy;

the light emitting region comprises Al_xIn_yGa_zP, wherein 0x<

1, 0<

y<

1, 0<

z<

1, and x+y+z=1; and

the separation is between about 1.12λ

_n and about 1.22λ

_n.

49. A far-field pattern of light intensity emitted from a light emitting diode as an article of manufacture, the pattern produced according to the method of claim 45.

50. The method of claim 45 wherein the light emitting region comprises multiple quantum wells and the separation is from a center of brightness of the multiple quantum wells to the reflector.

51. A far-field pattern of light intensity emitted from a light emitting diode as an article of manufacture, the pattern produced according to the method of claim 50.

36. A method of creating a light emitting diode, the method comprising:

selecting a material for a light emitting region capable of emitting radiation;

selecting a material for a reflector reflective of the radiation;

calculating a top escape cone of the light emitting diode;

determining a phase shift of the radiation when reflected off the reflector;

calculating a radiation pattern for at least one distance using the phase shift;

plotting extraction efficiency as a function of distance using the at least one radiation pattern; and

determining a separation distance corresponding a maximum in the plot of extraction efficiency as a function of distance.

38. A method of extracting light from the topside of a light emitting diode, the method comprising:

providing a light emitting region capable of emitting radiation; and

providing a reflector reflective of the radiation and separated from the light emitting region by a separation ranging between about 0.5λ

_n and about 0.9λ

_n, wherein λ

_n is the wavelength of the radiation emitted by the light emitting region within the region separating the light emitting region from the reflector.

45. A method of extracting light from the topside of a light emitting diode, the method comprising:

providing a light emitting region capable of emitting radiation; and

providing a reflector reflective of the radiation and separated from the light emitting region by a separation ranging between about λ

_n and about 1.4λ

_n, wherein λ

_n;

is the wavelength of the radiation emitted by the light emitting region within the region separating the light emitting region from the reflector.

52. A light emitting diode comprising:

a light emitting region capable of emitting radiation; and

a reflector reflective of the radiation, the reflector comprising one of gold and gold alloy;

wherein the reflector is separated from the light emitting region by a separation ranging between about 2.12λ

_n and about 2.3λ

_n, wherein λ

_n is the wavelength of the radiation within a region separating the light emitting region from the reflector.