LIGHT-EMITTING DIODES WITH INTEGRATED OPTICAL ELEMENTS

• US 20200135977A1
• Filed: 10/23/2019
• Published: 04/30/2020
• Est. Priority Date: 10/26/2018
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Raxium, Inc. (Alphabet Inc.)
• Inventors: LEUNG, Benjamin, TSAI, Miao-Chan, HURTT, Sheila, HE, Gang, SCHNEIDER, JR., Richard Peter
• Granted Patent: US 11,784,288 B2
• Time in Patent Office: Days
• CPC Class Codes: G02B 19/0019 having reflective surfaces only (e.g. louvre systems, systems with multiple planar reflectors)
• CPC Class Codes: G02B 19/0028 refractive and reflective surfaces, e.g. non-imaging catadioptric systems
• CPC Class Codes: G02B 19/0066 in the form of an LED array
• CPC Class Codes: G02B 27/30 Collimators
• CPC Class Codes: G02B 3/0056 arranged along two different directions in a plane, e.g. honeycomb arrangement of lenses G02B3/0043 takes precedence; miniaturised objectives for electronic devices employing wafer level optics G02B13/0085
• CPC Class Codes: G02B 3/04 with continuous faces that are rotationally symmetrical but deviate from a true sphere , e.g. so called "aspheric" lenses
• CPC Class Codes: H01L 25/0753 the devices being arranged next to each other
• CPC Class Codes: H01L 27/156 two-dimensional arrays
• CPC Class Codes: H01L 33/0008 having p-n or hi-lo junctions
• CPC Class Codes: H01L 33/18 within the light emitting region
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/325 characterised by the doping materials
• CPC Class Codes: H01L 33/58 Optical field-shaping elements
• CPC Class Codes: H01L 33/60 Reflective elements

Abstract

The disclosure describes various aspects of using optical elements monolithically integrated with light-emitting diode (LED) structures. In an aspect, a light emitting device includes a single LED structure having an active region and a single optical element disposed on the LED structure and configured to collimate and steer light emitted by the LED structure. One or more additional optical elements may also be disposed on the LED structure. In another aspect, a light emitting device may include multiple LED structures and a single optical element disposed on the multiple LED structures and configured to collimate and steer light emitted by the multiple LED structures. For each of these aspects, the LED structure(s) and the optical element(s) are made of a material that includes GaN, the LED structure(s) has a corresponding active region, and the LED structure(s) has a corresponding reflective contact disposed opposite to the optical element(s).

Claims

1. A light emitting device, comprising:

a light-emitting diode (LED) structure having an active region and made of a material including GaN, the active region having a p-side and an n-side;

an optical element disposed on the LED structure and made at least in part of a material including GaN, the optical element configured to collimate and steer a light emitted by the LED structure; and

a reflective contact disposed opposite to the optical element.

2. The light emitting device of claim 1, wherein the optical element is disposed closest to the n-side of the active region.

3. The light emitting device of claim 1, wherein the reflective contact is disposed closest to the p-side of the active region.

4. The light emitting device of claim 1, wherein the optical element is a convex lens.

5. The light emitting device of claim 1, wherein a shape of the optical element is one of a hemispherical shape or an aspherical shape.

6. The light emitting device of claim 5, wherein the aspherical shape is one of a hyperbolic shape, an ellipsoidal shape, or a parabolic shape.

7. The light emitting device of claim 1, wherein a size of the active region is smaller than a size of the optical element.

8. The light emitting device of claim 1, wherein a size of the active region is substantially the same as a size of the optical element.

9. The light emitting device of claim 1, wherein a shape of the optical element is asymmetric to steer the light emitted by the LED structure in a particular direction.

10. The light emitting device of claim 9, wherein the asymmetric shape of the optical element and the particular direction are based on a position of the light emitting device in an array of light emitting devices.

11. The light emitting device of claim 10, wherein the particular direction that the asymmetric shape of the optical element steers the light emitted by the LED structure is towards a center of the array of light emitting devices.

12. The light emitting device of claim 1, wherein the optical element has a submicron size.

13. The light emitting device of claim 1, wherein a size of the optical element ranges from 100 nm to 100 microns and this range includes one or more of the following subranges:

100 nm to 2 microns,

1 micron to 5 microns,

100 nm to 5 microns,

500 nm to 5 microns,

200 nm to 5 microns,

5 microns to 10 microns,

10 microns to 50 microns, or

25 microns to 100 microns.

14. The light emitting device of claim 1, wherein a distance from the optical element to the active region includes one or more of the following ranges:

100 nm to 2 microns,

0.5 microns to 3 microns,

1 micron to 10 microns,

1 micron to 20 microns,

1 micron to 25 microns,

1 micron to 50 microns, or

10 microns to 100 microns.

15. The light emitting device of claim 1, wherein the reflective contact is an electrically conductive contact disposed on a flat surface opposite the optical element and is configured to direct at least a portion of the light emitted by the LED structure towards the optical element.

16. The light emitting device of claim 1, wherein the active region of the LED structure and the optical element are part of a single crystalline material that includes GaN.

17. The light emitting device of claim 1, wherein the active region of the LED structure and the optical element are part of an epitaxially-grown material that includes GaN and has a continuous refractive index.

18. The light emitting device of claim 1, wherein the active region of the LED structure and the optical element are monolithically integrated.

19. The light emitting device of claim 1, wherein a position of the active region in the LED structure corresponds to a focal point of the optical element.

20. The light emitting device of claim 1, wherein the active region is laterally offset from the optical element.

21. The light emitting device of claim 20, wherein the offset is based on a position of the light emitting device in an array of light emitting devices.

22. The light emitting device of claim 21, wherein the offset is greater the farther the light emitting device is from a center of the array of light emitting devices.

23. The light emitting device of claim 1, wherein at least a portion of the LED structure is tapered such that tapered sidewalls are formed around the active region of the LED structure.

24. The light emitting device of claim 23, further comprising one or more materials disposed to cover at least a portion of the tapered sidewalls.

25. The light emitting device of claim 24, wherein the one or more materials include one or more of:

an absorber material,

a dielectric material, or

a metallic material.

26. The light emitting device of claim 24, wherein the one or more materials include one or more of:

a non-reflective material,

a material having angular dependent reflectivity, or

a highly reflective material.

27. The light emitting device of claim 24, wherein the one or more materials disposed on the tapered sidewalls are collectively configured to redirect at least a portion of light emitted by the LED structure towards the optical element.

28. The light emitting device of claim 1, wherein the material from which the LED structure is made includes InGaN.

29. The light emitting device of claim 1, wherein:

the light emitting device is one of multiple light emitting devices in an array, and

the array includes light emitting devices configured to produce one or more colors of light.

30. The light emitting device of claim 29, wherein the array is implemented as part of a display having one or more of the following capabilities:

ultra-high-resolution capabilities,

high dynamic range capabilities,

lightfield capabilities, or

high directionality.

31. The light emitting device of claim 1, wherein:

the optical element is a first optical element,

the light emitting device further comprises one or more additional optical elements disposed on the LED structure and made at least in part of a material including GaN, the one or more additional optical elements also being configured to collimate and steer the light emitted by the LED structure.

32. The light emitting device of claim 31, wherein the active region of the LED structure, the first optical element, and the one or more additional optical elements are part of a single crystalline material that includes GaN.

33. The light emitting device of claim 31, wherein the active region of the LED structure, the first optical element, and the one or more additional optical elements are part of an epitaxially-grown material that includes GaN and has a continuous refractive index.

34. The light emitting device of claim 31, wherein the active region of the LED structure, the first optical element, and the one or more additional optical elements are monolithically integrated.

35. The light emitting device of claim 31, wherein the light emitting device is a first light emitting device and is positioned adjacent to a second light emitting device that includes a single LED structure and a second optical element configured to collimate and steer a light emitted by the single LED structure.

36. The light emitting device of claim 35, wherein the first optical element of the first light emitting device is larger than the second optical element of the second light emitting device.

37. The light emitting device of claim 1, wherein at least a portion of the LED structure is separated from another LED structure by a trench within which there is included an optically non-transmissive material.

38. A light emitting device, comprising:

multiple light-emitting diode (LED) structures each having an active region and made of a material including GaN;

an optical element disposed on the multiple LED structures and made at least in part of a material including GaN, the optical element configured to collimate and steer a light emitted by the multiple LED structures; and

for each of the multiple LED structures, a reflective contact disposed opposite to the optical element.

39. The light emitting device of claim 38, wherein the multiple LED structures include LED structures configured to produce one or more colors of light.

40. The light emitting device of claim 38, wherein the multiple LED structures include a first LED structure configured to produce a first color of light, a second LED structure configured to produce a second color of light, and a third LED structure configured to produce a third color of light.

41. The light emitting device of claim 40, wherein:

the first color of light is green,

the second color of light is red, and

the third color of light is blue.

42. The light emitting device of claim 38, wherein:

the active region in each of the multiple LED structures includes a p-side and an n-side, and

the optical element is disposed closest to the n-side of the active regions.

43. The light emitting device of claim 38, wherein:

the active region in each of the multiple LED structures includes a p-side and an n-side, and

the reflective contact is disposed closest to the p-side of the active regions.

44. The light emitting device of claim 38, wherein the optical element is a convex lens.

45. The light emitting device of claim 38, wherein a shape of the optical element is one of a hemispherical shape or an aspherical shape.

46. The light emitting device of claim 45, wherein the aspherical shape is one of a hyperbolic shape, an ellipsoidal shape, or a parabolic shape.

47. The light emitting device of claim 38, wherein a shape of the optical element is asymmetric to steer the light emitted by the multiple LED structures in a particular direction.

48. The light emitting device of claim 47, wherein the asymmetric shape of the optical element and the particular direction are based on a position of the light emitting device in an array of light emitting devices.

49. The light emitting device of claim 48, wherein the particular direction that the asymmetric shape of the optical element steers the light emitted by the LED structure is towards a center of the array of light emitting devices.

50. The light emitting device of claim 38, wherein a size of the optical element ranges from 100 nm to 100 microns and this range includes at least one or more of the following subranges:

100 nm to 2 microns,

1 micron to 5 microns,

100 nm to 5 microns,

500 nm to 5 microns,

200 nm to 5 microns,

5 microns to 10 microns,

10 microns to 50 microns, or

25 microns to 100 microns.

51. The light emitting device of claim 38, wherein a distance from the optical element to the active region includes one or more of the following ranges:

100 nm to 2 microns,

0.5 microns to 3 microns,

1 micron to 10 microns,

1 micron to 20 microns,

1 micron to 25 microns,

1 micron to 50 microns, or

10 microns to 100 microns.

52. The light emitting device of claim 38, wherein for each of the multiple LED structures, the reflective contact is an electrically conductive contact disposed on a flat surface opposite the optical element and is configured to direct at least a portion of the light emitted by the respective LED structure towards the optical element.

53. The light emitting device of claim 38, wherein for each of the multiple LED structures, the active region of the respective LED structure and the optical element are part of a single crystalline material that includes GaN.

54. The light emitting device of claim 38, wherein for each of the multiple LED structures, the active region of the respective LED structure and the optical element are part of an epitaxially-grown material that includes GaN and has a continuous refractive index.

55. The light emitting device of claim 38, wherein for each of the multiple LED structures, the active region of the respective LED structure and the optical element are monolithically integrated.

56. The light emitting device of claim 38, wherein at least a portion of each of the multiple LED structures is tapered such that tapered sidewalls are formed around the active region of the respective LED structure.

57. The light emitting device of claim 56, further comprising one or more materials disposed to cover at least a portion of the tapered sidewalls.

58. The light emitting device of claim 57, wherein the one or more materials include one or more of:

an absorber material,

a dielectric material, or

a metallic material.

59. The light emitting device of claim 57, wherein the one or more materials include one or more of:

a non-reflective material,

a material having angular dependent reflectivity, or

a highly reflective material.

60. The light emitting device of claim 57, wherein the one or more materials disposed on the tapered sidewalls are collectively configured to redirect at least a portion of light emitted by the respective LED structure towards the optical element.

61. The light emitting device of claim 38, wherein the multiple LED structures include:

a first LED structure made of a material that includes InGaN with a first concentration of In and configured to produce a first color of light,

a second LED structure made of a material that includes InGaN with a second concentration of In and configured to produce a second color of light, and

a third LED structure made of a material that includes InGaN with a third concentration of In and configured to produce a third color of light.

62. The light emitting device of claim 38, wherein:

the light emitting device is one of multiple light emitting devices in an array, and

the array includes light emitting devices configured to produce the one or more colors of light.

63. The light emitting device of claim 62, wherein the array is implemented as part of a display having one or more of the following capabilities:

ultra-high-resolution capabilities,

high dynamic range capabilities,

lightfield capabilities, or

high directionality.

64. The light emitting device of claim 38, wherein at least a portion of one of the LED structures is separated from another one of the LED structures by a trench within which there is included an optically non-transmissive material.

65. The light emitting device of claim 38, wherein a number of the LED structures ranges from 10 to 200 LED structures.