Grown photonic crystals in semiconductor light emitting devices

• US 20060284187A1
• Filed: 06/17/2005
• Published: 12/21/2006
• Est. Priority Date: 06/17/2005
• 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., Gardner, Nathan F., Wierer, Jonathan J. Jr.
• Granted Patent: US 8,163,575 B2
• Time in Patent Office: Days
• US Class Current: 257/79
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: C30B 29/60 characterised by shape
• CPC Class Codes: G02B 6/1225 comprising photonic band-gap structures or photonic lattices
• 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 33/08 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 33/18 within the light emitting region
• CPC Class Codes: H01L 33/24 of the light emitting region, e.g. non-planar junction
• CPC Class Codes: H01S 5/11 Comprising a photonic bandgap structure
• CPC Class Codes: H01S 5/34333 with a well layer based on Ga(In)N or Ga(In)P, e.g. blue laser

Abstract

A photonic crystal is grown within a semiconductor structure, such as a III-nitride structure, which includes a light emitting region disposed between an n-type region and a p-type region. The photonic crystal may be multiple regions of semiconductor material separated by a material having a different refractive index than the semiconductor material. For example, the photonic crystal may be posts of semiconductor material grown in the structure and separated by air gaps or regions of masking material. Growing the photonic crystal, rather than etching a photonic crystal into an already-grown semiconductor layer, avoids damage caused by etching which may reduce efficiency, and provides uninterrupted, planar surfaces on which to form electric contacts.

Claims

1. A method comprising growing a photonic crystal within a semiconductor structure, the semiconductor structure comprising a light emitting region configured to emit light of wavelength λ

when forward biased, the light emitting region being disposed between an n-type region and a p-type region, wherein the photonic crystal comprises;

a plurality of regions of semiconductor material having a first refractive index; and

a plurality of regions of a material having a second refractive index, wherein the second refractive index is different from the first refractive index;

wherein the regions of material having a second refractive index are disposed between the regions of semiconductor material in an array, and each region of material having a second refractive index is located less than 5λ

from a nearest neighbor region of material having a second refractive index.

2. The method of claim 1 wherein the semiconductor structure is a III-nitride structure.

3. The method of claim 1 wherein the material having a second refractive index is air.

4. The method of claim 1 wherein the material having a second refractive index comprises one or more of air, an oxide of silicon, a nitride of silicon, an oxy-nitride of silicon, and a dielectric.

5. The method of claim 1 wherein growing a photonic crystal comprises:

forming on a semiconductor surface a mask having a plurality of openings; and

growing a semiconductor material through the openings.

6. The method of claim 5 wherein the semiconductor material grown through the openings comprises a plurality of semiconductor posts.

7. The method of claim 5 wherein the semiconductor material has a thickness greater than a thickness of the mask.

8. The method of claim 5 wherein the semiconductor material has a thickness substantially the same as a thickness of the mask.

9. The method of claim 5 further comprising providing a metal catalyst in the plurality of openings prior to growing the plurality of posts of semiconductor material.

10. The method of claim 5 wherein the metal catalyst is nickel.

11. The method of claim 5 further comprising growing a semiconductor layer having a substantially planar, uninterrupted top surface over the plurality of posts.

12. The method of claim 5 wherein the semiconductor structure is a first semiconductor structure, the method further comprising bonding a second semiconductor structure to the posts.

13. The method of claim 5 further comprising bonding a host substrate to the posts by a metal bonding layer disposed between the host substrate and the posts.

14. The method of claim 5 wherein the light emitting region is disposed within the posts.

15. The method of claim 5 further comprising prior to growing a plurality of posts, etching away a portion of the semiconductor surface to define a photonic crystal.

16. The method of claim 5 wherein the light emitting region is uninterrupted by the photonic crystal.

17. The method of claim 5 wherein the photonic crystal is formed in the n-type region.

18. The method of claim 5 wherein the photonic crystal is formed in the p-type region.

19. The method of claim 5 wherein the photonic crystal is a first photonic crystal formed in the n-type region, the method further comprising forming a second photonic crystal in the p-type region.

20. The method of claim 5 wherein at least one of the plurality of posts has a substantially constant diameter, substantially straight side walls, and grows perpendicular to a surface of a growth substrate.

21. The method of claim 1 wherein the regions of material having a second refractive index have a thickness of at least ¼

λ

.

22. The method of claim 1 wherein the regions of material having a second refractive index are located within 3λ

of the light emitting region.

23. The method of claim 1 wherein the plurality of regions of semiconductor material and the plurality of regions of material having a second refractive index are arranged in a lattice having a lattice constant between 0.1 λ

and 3 λ

.

24. The method of claim 1 wherein the plurality of regions of semiconductor material and the plurality of regions of material having a second refractive index are arranged in a lattice having a lattice constant between 0.1 λ

and λ

.

25. The method of claim 1 wherein:

the material having a second refractive index is air; and

the plurality of regions of semiconductor material and the plurality of regions of material having a second refractive index are arranged in a lattice having a lattice constant between from 0.35 λ and

0.55 λ

.

26. The method of claim 1 wherein the plurality of regions of semiconductor material and the plurality of regions of material having a second refractive index are arranged in a linear grating.

27. The method of claim 1 wherein the plurality of regions of semiconductor material and the plurality of regions of material having a second refractive index are arranged in a lattice, at least a portion of the lattice comprising one of a triangular, honeycomb, Archimedean, and quasi-crystal lattice.

28. The method of claim 27 wherein a radius of one of the regions of semiconductor material is 0.36 multipled by the lattice constant.

29. The method of claim 1 further comprising:

etching away a portion of the p-type region and the light emitting region to expose a portion of the n-type region;

forming electrical contacts on a remaining portion of the p-type region and the exposed portion of the n-type region; and

attaching the electrical contacts to a carrier.

30. The method of claim 29 wherein the semiconductor is grown on a growth substrate, the method further comprising:

filling a gap between the carrier and the semiconductor structure; and

removing the growth substrate.

31. The method of claim 1 wherein the semiconductor structure is grown on a growth substrate, the method further comprising:

attaching a surface of the semiconductor structure to a carrier; and

removing the growth substrate.

32. A device comprising:

a semiconductor structure comprising a light emitting layer configured to emit light of wavelength λ

, the light emitting layer being disposed between an n-type region and a p-type region, the semiconductor structure having a top surface and a bottom surface; and

a photonic crystal disposed within the semiconductor structure, the photonic crystal comprising;

a plurality of regions of semiconductor material having a first refractive index; and

a plurality of regions of a material having a second refractive index, wherein the second refractive index is different from the first refractive index;

wherein the regions of material having a second refractive index are disposed between the regions of semiconductor material in an array, and each region of material having a second refractive index is located less than 5 λ

from a nearest neighbor region of material having a second refractive index;

wherein the light emitting layer is disposed within the photonic crystal; and

wherein the top surface and the bottom surface of the semiconductor structure are uninterrupted by the photonic crystal.

33. The device of claim 32 wherein the light emitting layer is a III-nitride layer.

34. The device of claim 32 wherein the material having a second refractive index is air.

35. The device of claim 32 wherein the material having a second refractive index comprises one of an oxide of silicon, a nitride of silicon, an oxy-nitride of silicon, and a dielectric.

36. The device of claim 32 wherein the regions of material having a second refractive index have a thickness of at least ¼

λ

.

37. The device of claim 32 wherein the plurality of regions of semiconductor material and the plurality of regions of material having a second refractive index are arranged in a lattice having a lattice constant between 0.1 λ

and 3 λ

.

38. The device of claim 32 further comprising:

a first contact disposed on a bottom surface of the semiconductor structure; and

a second contact disposed on a top surface of the semiconductor structure.

39. The device of claim 32 wherein:

the top surface comprises a substantially planar surface;

a portion of the light emitting layer and one of the n-type region and the p-type region is removed from the bottom surface, such that the bottom surface includes an exposed portion of the n-type region and an exposed portion of the p-type region;

a first contact is formed on the exposed portion of the n-type region; and

a second contact is formed on the exposed portion of the p-type region.

40. A device comprising:

a semiconductor structure comprising a light emitting layer configured to emit light of wavelength λ

, the light emitting layer being disposed between an n-type region and a p-type region, the semiconductor structure having a top surface and a bottom surface; and

a photonic crystal disposed within the p-type region, the photonic crystal comprising;

a plurality of regions of semiconductor material having a first refractive index; and

a plurality of regions of a material having a second refractive index, wherein the second refractive index is different from the first refractive index;

wherein the regions of material having a second refractive index are disposed between the regions of semiconductor material in an array, and each region of material having a second refractive index is located less than 5 λ

from a nearest neighbor region of material having a second refractive index;

wherein the top surface and the bottom surface of the semiconductor structure are uninterrupted by the photonic crystal.

41. The device of claim 40 wherein the photonic crystal is a first photonic crystal, the device further comprising a second photonic crystal disposed within the n-type region.

42. The device of claim 40 wherein the light emitting layer is a III-nitride layer.

43. The device of claim 40 wherein the material having a second refractive index is air.

44. The device of claim 40 wherein the material having a second refractive index comprises one of an oxide of silicon, a nitride of silicon, an oxy-nitride of silicon, and a dielectric.

45. The device of claim 40 wherein the regions of material having a second refractive index have a thickness of at least ¼

λ

.

46. The device of claim 40 wherein the plurality of regions of semiconductor material and the plurality of regions of material having a second refractive index are arranged in a lattice having a lattice constant between 0.1 λ

and 3 λ

.

47. The device of claim 40 further comprising:

a first contact disposed on a bottom surface of the semiconductor structure; and

a second contact disposed on a top surface of the semiconductor structure.

48. The device of claim 40 wherein:

the top surface comprises a substantially planar surface;

a portion of the light emitting layer and one of the n-type region and the p-type region is removed from the bottom surface, such that the bottom surface includes an exposed portion of the n-type region and an exposed portion of the p-type region;

a first contact is formed on the exposed portion of the n-type region; and

a second contact is formed on the exposed portion of the p-type region.