Broad spectrum light emitting devices and methods and systems for fabricating the same

• US 20030089918A1
• Filed: 10/04/2002
• Published: 05/15/2003
• Est. Priority Date: 10/31/2001
• Status: Active Grant

• Current Assignee: CREE Led Incorporated (Smart Global Holdings Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Schwab, Scott, Hiller, Norbert, Negley, Gerald H.
• Granted Patent: US 7,858,403 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: H01L 27/156 two-dimensional arrays
• CPC Class Codes: H01L 33/508 having a non-uniform spatial arrangement or non-uniform concentration, e.g. patterned wavelength conversion layer, wavelength conversion layer with a concentration gradient of the wavelength conversion material

Abstract

Broad spectrum light emitting devices and methods and systems for fabricating such devices are provide. Such devices may include a light emitting element, such as a diode or laser, which emits light in a predefined range of frequencies, and luminous material on the light emitting diode. The characteristics of the luminous material, such as the amount, composition and/or doping of the luminous material or materials may be based on measured light output of the light emitting device, such as the measured output frequency and/or power of the light emitting device.

Claims

1. A method of fabricating a light emitting apparatus, comprising:

measuring light output of a semiconductor light emitting device; and

tailoring at least one characteristic of luminous material applied to the light emitting device based on the measured light output of the light emitting device.

2. The method of claim 1, wherein tailoring at least one characteristic comprises selectively removing luminous material to the light emitting device based on the measured output of the light emitting device.

3. The method of claim 1, wherein tailoring at least one characteristic comprises selectively applying luminous material to the light emitting device based on the measured output of the light emitting device.

4. The method of claim 3, wherein selectively applying luminous material comprises selectively applying an amount of luminous material to the light emitting device based on the measured light output of the light emitting device.

5. The method of claim 3, wherein selectively applying luminous material comprises selectively applying different compositions of luminous material to the light emitting device based on the measured light output of the light emitting device.

6. The method of claim 3, wherein selectively applying luminous material comprises selectively applying differing doping levels of luminous material to the light emitting device based on the measured light output of the light emitting device.

7. The method of claim 3, wherein measuring light output of the light emitting device is preceded by applying a coating of luminous material to the light emitting device.

8. The method of claim 3, wherein selectively applying luminous material is preceded by singulating the light emitting device from a wafer having a plurality of light emitting devices.

9. The method of claim 8, wherein singulating the light emitting devices is followed by grouping the singulated light emitting devices based on measured light output of respective ones of the singulated light emitting devices;

and

wherein selectively applying luminous material comprises applying at least one of different amounts of luminous material, differently doped luminous material and/or different composition luminous material to different groups of the singulated light emitting devices.

10. The method of claim 8, wherein measuring light output of the light emitting device is preceded applying a coating of luminous material to the light emitting device.

11. The method of claim 3, wherein selectively applying luminous material comprises selectively applying luminous material utilizing at least on of an inkjet application process, an air brush application process, a fluid application process, electrostatic deposition, electrophoretic deposition, screen printing, dipping, roll coating and/or vacuum deposition.

12. The method of claim 3, further comprising repeating the measurement of light output and the selective application of luminous material until the measured light output of the light emitting device meets a predefined criteria.

13. The method of claim 1, wherein the light emitting device comprises a light emitting device on a wafer having a plurality of light emitting devices.

14. The method of claim 1, wherein the light emitting device is a gallium nitride based light emitting device.

15. The method of claim 14, wherein the light emitting device has a silicon carbide substrate where light is extracted through the silicon carbide substrate and wherein the luminous material is applied to the silicon carbide substrate.

16. The method of claim 1, wherein the measured light output comprises at least one of a frequency of light output and/or a power of light output.

17. A method of fabricating a light emitting apparatus, comprising:

measuring light output of respective ones of a plurality of semiconductor light emitting devices; and

tailoring luminous material on at least one of the respective ones of the plurality of light emitting devices based on the measured light output of the respective ones of the light emitting devices.

18. The method of claim 17, wherein tailoring luminous material comprises selectively removing luminous material from at least one of the respective ones of the plurality of light emitting devices based on the measured light output of the respective ones of the light emitting devices.

19. The method of claim 17, wherein tailoring luminous material comprises selectively applying luminous material to least one of the respective ones of the plurality of light emitting devices based on the measured light output of the respective ones of the light emitting devices.

20. The method of claim 17, wherein measuring light output of respective ones of the plurality of light emitting devices comprises:

activating respective ones of the plurality of light emitting devices; and

measuring light output of the respective ones of the plurality of light emitting devices when the respective ones of the light emitting devices are activated.

21. The method of claim 20, wherein activating respective ones of the plurality of light emitting devices comprises activating respective ones of the plurality of light emitting devices individually.

22. The method of claim 20, wherein activating respective ones of the plurality of light emitting devices comprises activating respective ones of the plurality of light emitting devices in groups.

23. The method of claim 20, wherein activating respective ones of the plurality of light emitting devices comprises activating respective ones of the plurality of light emitting devices sequentially.

24. The method of claim 20, wherein activating respective ones of the plurality of light emitting devices comprises activating respective ones of the plurality of light emitting devices in parallel.

25. The method of claim 20, wherein the respective ones of the plurality of light emitting devices where have two contacts accessible from a single side of the device, and wherein activating respective ones of the plurality of light emitting devices comprise:

placing the respective ones of the plurality of light emitting devices on a conductive foil; and

contacting the respective ones of the plurality of light emitting devices through the foil.

26. The method of claim 19, further comprising generating a map of the light output of the respective ones of the light emitting devices;

and

wherein selectively applying luminous material to at least one of the respective ones of the plurality of light emitting devices based on the measured light output of the respective ones of the light emitting devices comprises selectively applying luminous material to at least one of the respective ones of the plurality of light emitting devices based on the measured light output of the respective ones of the light emitting devices utilizing the generated map.

27. The method of claim 19, further comprising repeating the measurement of light output of the respective ones of the plurality of light emitting devices and the selective application of luminous material until a predefined light output criteria is reached.

28. The method of claim 27, wherein the predefined light output criteria comprises a substantially uniform light output of the plurality of light emitting devices.

29. The method of claim 27, wherein the predefined light output criteria comprises a threshold percentage of the plurality of light emitting devices having a predefined light output.

30. The method of claim 19, wherein measuring light output of respective ones of the plurality of light emitting devices is preceded by applying a coating of luminous material to the plurality of light emitting devices.

31. The method of claim 19, wherein selectively applying luminous material comprises selectively applying an amount of luminous material to at least one of the respective ones of the light emitting devices based on the measured light output of the respective ones of the light emitting devices.

32. The method of claim 19, wherein selectively applying luminous material comprises selectively applying different compositions of luminous material to the respective ones of the light emitting devices based on the measured light output of the respective ones of the light emitting devices.

33. The method of claim 19, wherein selectively applying luminous material comprises selectively applying differing doping levels of luminous material to the respective ones of the light emitting devices based on the measured light output of the respective ones of the light emitting devices.

34. The method of claim 19, wherein selectively applying luminous material comprises selectively applying luminous material utilizing at least one of an inkjet application process, an air brush application process, a fluid application process, electrostatic deposition, electrophoretic deposition, screen printing, dipping, roll coating and/or vacuum deposition.

35. The method of claim 19, wherein the respective ones of the plurality of light emitting devices comprise singulated light emitting devices;

and

wherein selectively applying luminous material comprises;

sorting the singulating light emitting devices based on the measured light output of the light emitting devices so as to group singulated light emitting devices having common measured light output characteristics; and

selectively applying luminous material to the singulated light emitting devices so as to provide different luminous material characteristics to different groups of singulated light emitting devices.

36. The method of claim 35, wherein the different luminous material characteristics comprise at least one of different amounts of luminous material, different dopings of luminous material and/or different compositions of luminous material.

37. The method of claim 17, wherein the plurality of light emitting devices comprise a plurality of light emitting devices on a wafer.

38. The method of claim 37, wherein the light emitting devices comprise gallium nitride based light emitting devices.

39. The method of claim 38, wherein the wafer comprises a silicon carbide wafer.

40. The method of claim 17, wherein the measured light output comprises at least one of a frequency of light output and/or a power of light output.

41. A solid state light emitting apparatus, comprising:

an individual solid state light emitting device having at least one measurable optical characteristic; and

a coating of luminous material on the light emitting device, the coating of luminous material having characteristics selected based on a measurement of the optical characteristics of the light emitting device to provide a predefined output characteristic of the individual light emitting device.

42. The apparatus of claim 41, wherein the coating of luminous material comprises:

a first coating of luminous material applied independent of the measured optical characteristics; and

a second coating of luminous material applied based on the measured optical characteristics.

43. The apparatus of claim 42, wherein the first coating and the second coating are of the same composition luminous material and wherein a thickness of the second coating is selected based on the measured optical characteristics.

44. The apparatus of claim 42, wherein the first coating and the second coating are of different composition luminous material and wherein the composition of the second coating is selected based on the measured optical characteristics.

45. The apparatus of claim 42, wherein doping of the second coating is selected based on the measured optical characteristics.

46. The apparatus of claim 42, wherein the measured optical characteristics are optical characteristics of the light emitting device with the first coating of luminous material applied.

47. The apparatus of claim 41, wherein a composition of the luminous material is selected based on the measured optical characteristics.

48. The apparatus of claim 41, wherein the light emitting device is a gallium nitride based light emitting device.

49. The apparatus of claim 48, wherein the light emitting device further comprises a silicon carbide substrate and wherein the coating of luminous material is on the silicon carbide substrate.

50. The apparatus of claim 48, wherein the luminous material comprises YAG:

Ce.

51. A light emitting apparatus, comprising:

a plurality of light emitting devices on at least a portion of a wafer; and

coatings of luminous material on respective ones of the plurality of light emitting devices, the coatings of luminous material on the respective ones of the plurality of light emitting devices having different characteristics.

52. The apparatus of claim 51, wherein the different characteristics comprise at least one of different amounts of luminous material, different dopings of a luminous material and/or different compositions of luminous material.

53. The apparatus of claim 51, wherein the coating of luminous material comprises:

a first coating of luminous material on each of the respective ones of the plurality of light emitting devices; and

a second coating of luminous material applied based on a measured optical characteristic of respective ones of the plurality of light emitting devices.

54. The apparatus of claim 53, wherein the first coating and the second coating are of the same composition luminous material and wherein a thickness of the second coating is selected based on the measured optical characteristics.

55. The apparatus of claim 53, wherein the first coating and the second coating are of different composition luminous material and wherein the composition of the second coating is selected based on the measured optical characteristics.

56. The apparatus of claim 53, wherein doping of the second coating is selected based on the measured optical characteristics.

57. The apparatus of claim 53, wherein the measured optical characteristics are optical characteristics of respective ones of the light emitting devices with the first coating of luminous material applied.

58. The apparatus of claim 51, wherein a composition of the coating of luminous material differs between the respective ones of the plurality of light emitting devices based on measured optical characteristics of the respective ones of the plurality of light emitting devices.

59. The apparatus of claim 51, wherein a thickness of the coating of luminous material differs between the respective ones of the plurality of light emitting devices based on measured optical characteristics of the respective ones of the plurality of light emitting devices.

60. The apparatus of claim 51, wherein a doping of the coating of luminous material differs between the respective ones of the plurality of light emitting devices based on measured optical characteristics of the respective ones of the plurality of light emitting devices.

61. The apparatus of claim 51, wherein the light emitting device is a gallium nitride based light emitting device.

62. The apparatus of claim 61, wherein the light emitting device further comprises a silicon carbide substrate and wherein the coating of luminous material is on the silicon carbide substrate.

63. The apparatus of claim 61, wherein the luminous material comprises YAG:

Ce.

64. A system for fabricating light emitting devices, comprising:

a lighting element activation circuit configured to activate light emitting devices;

an output measurement circuit configured to measure the light output by the activated light emitting devices;

a luminous material application device configured to selectively applying luminous material to light emitting devices; and

a controller operably associated with the output measurement circuit and the luminous material application device and configured to control the luminous material application device to selectively apply luminous material to light emitting devices based on the measured light output of the activated light emitting devices.

65. The system of claim 64, wherein the luminous material application device comprises at least one of an inkjet application system, an air brush application system, a fluid application system, an electrostatic deposition system, an electrophoretic deposition system, a screen printing system, a dipping system, a roll coating system and/or vacuum deposition system.

66. The system of claim 64, wherein the controller is further configured to control the luminous material application device to apply a coating of luminous material prior to measurement of the output of the activated light emitting devices.

67. The system of claim 64, wherein the luminous material application device is configured to selectively apply at least one of different amounts of luminous material, different dopings of luminous material and/or different compositions of luminous material.