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

• US 6,903,376 B2
• Filed: 05/29/2002
• Issued: 06/07/2005
• Est. Priority Date: 12/22/1999
• Status: Expired due to Term

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Lumileds Lighting US LLC (Apollo Global Management, Inc.)
• Inventors: Shen, Yu-Chen, Krames, Michael R., Ludowise, Michael J.
• Primary Examiner(s): Nelms, David
• Assistant Examiner(s): Nguyen, Thinh T
• Application Number:
  US10/158,360
• Publication Number:
  US 20020190260A1
• Time in Patent Office: 1,105 Days
• Field of Search: 257/81, 257/12, 257/13, 257/14.15, 257/22, 257/94, 257/431, 315/150, 214/24
• 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

_n 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 nm 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_zN, 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 1.3λ

_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 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.

36. 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.