Semiconductor light emitting device and method for fabricating the same

• US 20050184305A1
• Filed: 02/18/2005
• Published: 08/25/2005
• Est. Priority Date: 02/19/2004
• Status: Active Grant

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Ueda, Tetsuzo
• Granted Patent: US 7,569,863 B2
• Time in Patent Office: Days
• US Class Current: 257/99
• CPC Class Codes: H01L 2224/05001 Internal layers
• CPC Class Codes: H01L 2224/05017 comprising protrusions or indentations
• CPC Class Codes: H01L 2224/05023 the whole internal layer protruding from the surface
• CPC Class Codes: H01L 2224/05111 Tin [Sn] as principal constituent
• CPC Class Codes: H01L 2224/05124 Aluminium [Al] as principal constituent
• CPC Class Codes: H01L 2224/05144 Gold [Au] as principal constituent
• CPC Class Codes: H01L 2224/05155 Nickel [Ni] as principal constituent
• CPC Class Codes: H01L 2224/05169 Platinum [Pt] as principal constituent
• CPC Class Codes: H01L 2224/05558 conformal layer on a patterned surface
• CPC Class Codes: H01L 2224/05568 the whole external layer protruding from the surface
• CPC Class Codes: H01L 2224/05644 Gold [Au] as principal constituent
• CPC Class Codes: H01L 2224/0603 Bonding areas having different sizes, e.g. different heights or widths
• CPC Class Codes: H01L 2224/06102 the bonding areas being at different heights
• CPC Class Codes: H01L 2224/14 of a plurality of bump connectors
• CPC Class Codes: H01L 2224/1703 Bump connectors having different sizes, e.g. different diameters, heights or widths
• CPC Class Codes: H01L 24/03 Manufacturing methods
• CPC Class Codes: H01L 24/05 of an individual bonding area
• CPC Class Codes: H01L 24/16 of an individual bump connector
• 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 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

Abstract

A semiconductor light emitting device is composed of a blue light emitting diode, a red light emitting layer grown epitaxially on the blue light emitting diode, and an insulating material containing a YAG fluorescent material. The red light emitting layer is made of, e.g., undoped In_0.4Ga_0.6N having a forbidden band width of 1.9 eV and formed on a p-type semiconductor layer to have a configuration consisting of a plurality of mutually spaced-apart islands.

Claims

1. A semiconductor light emitting device comprising:

a light emitting diode for emitting first emission light; and

a semiconductor film provided in a portion of the light emitting diode to absorb the first emission light and emit second emission light,

wherein in the semiconductor film emits the second emission light through optical excitation by the first emission light.

2. The semiconductor light emitting device of claim 1, further comprising:

a transparent electrode provided in the light emitting diode,

wherein the transparent electrode transmits the first emission light or the second emission light.

3. The semiconductor light emitting device of claim 1, wherein the semiconductor film is formed on a part of a light emitting surface of the semiconductor light emitting device.

4. The semiconductor light emitting device of claim 1, further comprising:

a fluorescent material covering the light emitting diode and the semiconductor film,

wherein the fluorescent material absorbs the first emission light and emits third emission light.

5. The semiconductor light emitting device of claim 1, wherein the light emitting diode or the semiconductor film is formed on a substrate made of a single crystal.

6. The semiconductor light emitting device of claim 5, wherein the substrate transmits the first emission light and the second emission light.

7. The semiconductor light emitting device of claim 2, wherein the transparent electrode is provided with a plurality of openings and the semiconductor film is formed in each of the openings on a light emitting surface of the light emitting diode.

8. The semiconductor light emitting device of claim 7, wherein the semiconductor film is formed in mutually divided relation in each of the openings on a light emitting surface of the light emitting diode.

9. The semiconductor light emitting device of claim 7, wherein the semiconductor film is formed to cover a part of the transparent electrode in the vicinity of the openings.

10. The semiconductor light emitting device of claim 9, wherein the semiconductor film has a crystal defect density which is lower in the portion thereof located on the transparent electrode than in each of the portions thereof located over the individual openings of the transparent electrode.

11. The semiconductor light emitting device of claim 1, wherein the first emission light is blue light or ultraviolet light.

12. The semiconductor light emitting device of claim 11, wherein the semiconductor film is excited by the first emission light to emit the second emission light which is red light.

13. The semiconductor light emitting device of claim 1, wherein the semiconductor film is composed of a plurality of semiconductor films which are stacked in layers and emit emission light components having different wavelengths from each of the stacked layers.

14. The semiconductor light emitting device of claim 1, wherein the semiconductor film is doped with impurities and excited by the first emission light to emit the second emission light in a visible range via energy levels resulting from the impurities.

15. The semiconductor light emitting device of claim 1, wherein the semiconductor film is doped with an impurity to emit the second emission light in a visible range through light emission from inner-shell transition of the impurities.

16. The semiconductor light emitting device of claim 15, wherein the impurity is Eu, Sm, or Yb.

17. The semiconductor light emitting device of claim 15, wherein the impurities in the semiconductor film are introduced by ion implantation.

18. The semiconductor light emitting device of claim 5, wherein the single crystal is sapphire, silicon carbide, gallium nitride, aluminum nitride, magnesium oxide, lithium gallium oxide, lithium aluminum oxide, lithium aluminum oxide, or a mixed crystal of lithium gallium oxide and lithium aluminum oxide.

19. The semiconductor light emitting device of claim 1, further comprising a metal film provided in the light emitting diode and having a thickness of at least 10 μ

m, wherein a current is injected in the light emitting diode through the metal film.

20. The semiconductor light emitting device of claim 19, wherein the metal film is made of gold, copper, or silver.

21. The semiconductor light emitting device of claim 1, wherein the light emitting diode is provided with a metal electrode having a reflectivity of 60% or more with respect to the first emission light or the second emission light.

22. The semiconductor light emitting device of claim 21, wherein the metal electrode is composed of a single-layer film or a multi-layer film each made of at least one material selected from the group consisting of gold, platinum, copper, silver, and rhodium.

23. A method for fabricating a semiconductor light emitting device, the method comprising the steps of:

(a) forming a light emitting diode composed of a plurality of semiconductor layers on a substrate made of a single crystal; and

(b) selectively forming, on the light emitting diode, a semiconductor film which absorbs first emission light and emits second emission light through the optical excitation by the first emission light.

24. The method of claim 23, further comprising the step of:

(c) between the steps (a) and (b) or after the step (b), forming a transparent electrode which transmits the first emission light on the light emitting diode.

25. The method of claim 24, wherein the step (c) includes the step of providing a plurality of openings in the transparent electrode.

26. The method of claim 25, wherein the semiconductor film is formed in the step (b) to selectively grow from each of the regions of an upper surface of the light emitting diode which are exposed through the plurality of openings of the transparent electrode.

27. The method of claim 23, further comprising the step of:

(d) after the step (b), irradiating the surface of the substrate opposite to the light emitting diode with light having a wavelength which is not absorbed by the substrate but is absorbed by the semiconductor layers composing the light emitting diode to separate the substrate from the diode.

28. The method of claim 27, wherein the step (d) includes forming, in a part of the semiconductor layers irradiated with the light, a decomposition layer resulting from thermal decomposition of the irradiated semiconductor layers.

29. The method of claim 27, further comprising the step of:

(e) after the step (d), forming a metal film on the light emitting diode or on the semiconductor film.

30. A method for fabricating a semiconductor light emitting device, the method comprising the steps of:

(a) forming a semiconductor film on a substrate made of a single crystal; and

(b) forming a light emitting diode composed of a plurality of semiconductor layers on the semiconductor film, wherein

the semiconductor film absorbs first emission light emitted from the light emitting diode and emits second emission light through the optical excitation by the first emission light.

31. The method of claim 30, further comprising the step of:

(c) between the steps (a) and (b), forming a transparent electrode which transmits the first emission light on the semiconductor film.

32. The method of claim 31, wherein the step (c) includes the step of providing a plurality of openings in the transparent electrode.

33. The method of claim 32, wherein a lower one of the plurality of semiconductor layers is formed in the step (b) to selectively grow from each of the regions of an upper surface of the semiconductor film which are exposed through the plurality of openings of the transparent electrode.

34. The method of claim 30, further comprising the step of:

(d) after the step (b), irradiating the surface of the substrate opposite to the semiconductor film with light having a wavelength which is not absorbed by the substrate but is absorbed by the semiconductor film to separate the substrate from the semiconductor film.

35. The method of claim 34, wherein the step (d) includes forming, in a part of the semiconductor layers irradiated with the light, a decomposition layer resulting from thermal decomposition of the irradiated semiconductor layers.

36. The method of claim 34, further comprising the step of:

(e) after the step (d), forming a metal film on the light emitting diode or on the semiconductor film.

37. A semiconductor light emitting device comprising:

a light emitting diode composed of a first n-type semiconductor layer, a p-type semiconductor layer, and a second n-type semiconductor layer which are formed successively to emit first emission light; and

a semiconductor film provided in the light emitting diode to absorb the first emission light and emit second emission light through the optical excitation by the first emission light, wherein

when a voltage is applied such that the second n-type semiconductor layer has a positive potential relative to the first n-type semiconductor layer, a current flows from the second n-type semiconductor layer to the first n-type semiconductor layer.

38. The semiconductor light emitting device of claim 37, wherein an impurity concentration in each of the p-type semiconductor layer and the second n-type semiconductor layer is 10¹⁸ cm⁻

3 or more.

39. The semiconductor light emitting device of claim 37, further comprising:

a fluorescent material covering the light emitting diode and the semiconductor film which absorbs the first emission light and emits third emission light through the optical excitation by the first emission light.

40. The semiconductor light emitting device of claim 37, wherein the light emitting diode or the semiconductor film is formed on a substrate made of a single crystal.

41. The semiconductor light emitting device of claim 37, further comprising:

a metal film provided on the light emitting diode to have a thickness of at least 10 μ

m, wherein

an operating current is injected in the light emitting diode through the metal film.

42. The semiconductor light emitting device of claim 37, wherein the light emitting diode is provided with a metal electrode having a reflectivity of 60% or more with respect to the first emission light or the second emission light.

43. The semiconductor light emitting device of claim 37, wherein the first emission light is blue light or ultraviolet light.

44. The semiconductor light emitting device of claim 37, wherein the second emission light is red light.

45. The semiconductor light emitting device of claim 37, wherein the semiconductor film is composed of a plurality of semiconductor films which are stacked in layers and emit emission light components having different wavelengths from each of the stacked layers.

46. The semiconductor light emitting device of claim 37, wherein the semiconductor film is doped with impurities and the semiconductor film is excited by the first emission light to emit the second emission light in a visible range via energy levels resulting from the impurities.

47. The semiconductor light emitting device of claim 37, wherein the semiconductor film is doped with impurities to emit the second emission light in a visible range through light emission from inner-shell transition of the impurities.

48. The semiconductor light emitting device of claim 47, wherein the impurity is Eu, Sm, or Yb.

49. The semiconductor light emitting device of claim 47, wherein the impurities in the semiconductor film are introduced by ion implantation.

50. The semiconductor light emitting device of claim 41, wherein the metal film is made of gold, copper, or silver.

51. The semiconductor light emitting device of claim 42, wherein the metal electrode is composed of a single-layer film or a multi-layer film each made of at least one material selected from the group consisting of gold, platinum, copper, silver, and rhodium.

52. A method for fabricating a semiconductor light emitting device, the method comprising the steps of:

(a) successively depositing a first n-type semiconductor layer, a p-type semiconductor layer, and a second n-type semiconductor layer on a substrate made of a single crystal to form a light emitting diode; and

(b) selectively forming, on the light emitting diode, a semiconductor film which absorbs first emission light emitted from the light emitting diode and emits second emission light through the optical excitation by the first emission light, wherein

an impurity concentration in each of the p-type semiconductor layer and the second n-type semiconductor layer is set in the step (a) to allow a current to flow from the second n-type semiconductor layer to the first n-type semiconductor layer when a voltage is applied such that the second n-type semiconductor layer has a positive potential relative to the first n-type semiconductor layer.

53. The method of claim 52, wherein the impurity concentration in each of the p-type semiconductor layer and the second n-type semiconductor layer is 10¹⁸ cm⁻

3 or more.

54. The method of claim 52, further comprising the step of:

(c) after the step (b), separating the substrate from the light emitting diode.

55. The method of claim 54, wherein the step (c) includes the step of irradiating the surface of the substrate opposite to the light emitting diode with light having a wavelength which is not absorbed by the substrate but is absorbed by the semiconductor layers composing the light emitting diode to form, in a part of the semiconductor layers irradiated with the light, a decomposition layer resulting from decomposition of the semiconductor layers.

56. The method of claim 55, further comprising the steps of:

(d) prior to the step (c), bonding a holding substrate made of a material other than that of the substrate to the light emitting diode or to the semiconductor film; and

(e) after the step (c), separating the holding substrate from the light emitting diode or from the semiconductor film.