Light emitting device including arrayed emitters defined by a photonic crystal

• US 7,697,584 B2
• Filed: 10/02/2006
• Issued: 04/13/2010
• Est. Priority Date: 10/02/2006
• Status: Active Grant

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Philips Lumileds Lighting Company LLC (Apollo Global Management, Inc.)
• Inventors: Wierer, Jonathan J. Jr., Sigalas, Mihail M.
• Primary Examiner(s): Harvey; Minsun
• Assistant Examiner(s): Park; Kinam
• Application Number:
  US11/537,940
• Publication Number:
  US 20080080581A1
• Time in Patent Office: 1,289 Days
• Field of Search: 372/45.01, 372/46.01, 372/43.01, 372/22, 372/21, 372/23
• US Class Current: 372/45.01
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2933/0083 Periodic patterns for optical field-shaping in or on the semiconductor body or semiconductor body package, e.g. photonic bandgap structures
• CPC Class Codes: H01L 33/0093 Wafer bonding; Removal of the growth substrate
• CPC Class Codes: H01L 33/145 with a current-blocking structure
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/24 of the light emitting region, e.g. non-planar junction
• CPC Class Codes: H01L 33/405 Reflective materials
• 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

Abstract

A light emitting device includes a structure with a light emitting region disposed between an n-type region and a p-type region. A plurality of holes in the structure, which form a photonic crystal, are formed in a first region of the structure corresponding to a first portion of the light emitting region. A second region of the structure corresponding to a second portion of the light emitting region is free of holes. The device is configured such that when forward biased, current is injected in the second region and the first region is substantially free of current.

Claims

1. A device comprising:

a structure including a light emitting region disposed between an n-type region and a p-type region; and

a reflector disposed on at least a portion of a bottom surface of the structure, wherein;

a plurality of holes in the structure are formed in a first region of the structure corresponding to a first portion of the light emitting region;

a plurality of second regions of the structure, each second region corresponding to a second portion of the light emitting region, are free of holes;

each of the second regions is surrounded by the first region;

in areas of the structure disposed between individual holes, a nonconductive material is disposed between the light emitting region and the reflector; and

the device is configured such that when forward biased, current is injected in the second regions and at least a portion of the first region is substantially free of current.

2. The device of claim 1 wherein a majority of light extracted from the structure is emitted from the first region.

3. The device of claim 1 wherein a majority of light extracted from the structure is emitted from the plurality of second regions.

4. The device of claim 1 wherein light extracted from the structure is emitted from both the first region and the plurality of second regions.

5. The device of claim 1 wherein a majority of light extracted from the structure is extracted through a top surface of the structure.

6. The device of claim 1 wherein the plurality of holes form a photonic crystal comprising a periodic variation in index of refraction.

7. The device of claim 1 wherein the nonconductive material comprises an implanted layer or an oxide layer.

8. The device of claim 1 wherein the structure comprises a III-nitride semiconductor structure.

9. The device of claim 1 wherein the holes extend into light emitting region.

10. The device of claim 1 wherein the holes extend into the n-type region.

11. The device of claim 1 wherein the holes extend into the p-type region.

12. The device of claim 1 wherein the holes extend through an entire thickness of the structure.

13. The device of claim 1 wherein openings to the holes are disposed in a top surface of the structure and the holes extend toward a bottom surface of the structure.

14. The device of claim 1 wherein openings to the holes are disposed in a bottom surface of the structure and the holes extend toward a top surface of the structure.

15. The device of claim 1 wherein the reflector comprises silver.

16. The device of claim 1 wherein the reflector is a first contact electrically connected to the p-type region, the device further comprising a second contact electrically connected to the n-type region proximate a top surface of the structure.

17. The device of claim 16 further comprising a conductive oxide disposed between one of the first and second contacts and the structure.

18. The device of claim 17 wherein the conductive oxide is one of indium tin oxide, InO:

Ga, and ZnO;

Ga.

19. The device of claim 1 wherein the reflector is a first contact electrically connected to the p-type region, the device further comprising a second contact electrically connected to the n-type region, wherein the second contact is disposed in a via formed in the bottom surface of the structure.

20. The device of claim 19 wherein the plurality of holes are disposed proximate the bottom surface of the structure.

21. The device of claim 19 wherein the plurality of holes are disposed proximate a top surface of the structure.

22. The device of claim 1 wherein at least one of the second regions has a lateral extent between 0.15 μ

m and 3 μ

m.

23. The device of claim 1 wherein each of the plurality of second regions is spaced between 0.3 μ

m and 10 μ

m from its nearest neighbor second region.

24. The device of claim 1 wherein a maximum thickness of the structure is less than 500 nm.

25. The device of claim 1 wherein the plurality of holes are formed in a lattice having a lattice constant between 200 nm and 500 nm.

26. The device of claim 1 wherein the plurality of holes are formed in a lattice, wherein the lattice is one of triangular, square, hexagonal, honeycomb, and quasi-crystal.

27. The device of claim 1 wherein the plurality of holes are formed in a lattice having a lattice constant;

and

a ratio of a radius of at least one hole to the lattice constant ranges between 0.2 and 0.45.

28. The device of claim 1 further comprising:

leads electrically connected to the n-type and p-type regions; and

a cover disposed over the structure.

29. The device of claim 1 further comprising a wavelength-converting material disposed in a path of light extracted from the structure.

30. The device of claim 29 wherein:

when forward biased, the light emitting region emits light of a first wavelength;

the wavelength-converting material is configured to absorb at least a portion of the light of a first wavelength and emit light of at least one second wavelength; and

composite light comprising light of the first wavelength and light of the second wavelength appears white.

31. The device of claim 29 wherein:

when forward biased, the light emitting region emits light of a first wavelength;

the wavelength-converting material is configured to absorb at least a portion of the light of a first wavelength and emit light of a second wavelength; and

after passing through the wavelength-converting material, light escaping the device appears the color of the second wavelength.

32. The device of claim 31 wherein the second wavelength is red, green, or blue.

33. The device of claim 1 further comprising a first contact electrically connected to the n-type region and a second contact electrically connected to the p-type region, wherein the first and second contacts are configured such that when forward biased, current is injected into each of the second regions.

34. The device of claim 1 wherein:

the plurality of holes formed in the first region of the structure are arranged in a lattice; and

each of the second regions of the structure, which are free of holes, comprises a region wherein a hole at least one lattice position is omitted.

35. The device of claim 1 wherein:

the first region comprises holes formed in a lattice and areas of III-nitride material separating individual holes; and

a lateral extent of each second region is larger than a lateral extent of the III-nitride material separating nearest neighbor holes in the first region.