Light emitting apparatus

• US 20050062060A1
• Filed: 08/23/2004
• Published: 03/24/2005
• Est. Priority Date: 08/26/2003
• Status: Active Grant

• Current Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Original Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Inventors: Yoshimoto, Susumui, Akita, Katsushi, Sakurada, Takashi, Katayama, Koji, Nakamura, Takao, Kiyama, Makoto, Nagai, Youichi, Uematsu, Koji, Ikeda, Ayako
• Granted Patent: US 7,202,509 B2
• Time in Patent Office: Days
• US Class Current: 257/100
• CPC Class Codes: H01L 2224/05573 Single external layer
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/06102 the bonding areas being at different heights
• CPC Class Codes: H01L 2224/16245 the item being metallic
• CPC Class Codes: H01L 2224/1703 Bump connectors having different sizes, e.g. different diameters, heights or widths
• CPC Class Codes: H01L 2224/32245 the item being metallic
• CPC Class Codes: H01L 2224/45015 being circular
• CPC Class Codes: H01L 2224/45099 Material
• CPC Class Codes: H01L 2224/45139 Silver (Ag) as principal constituent
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/48257 connecting the wire to a die pad of the item
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2224/8592 Applying permanent coating, e.g. protective coating
• 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 2924/00011 Not relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• 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 2924/01049 Indium [In]
• CPC Class Codes: H01L 2924/20752 : larger or equal to 20 microns less than 30 microns
• CPC Class Codes: H01L 2924/2076 : equal to or larger than 100 microns
• CPC Class Codes: H01L 2924/3025 : Electromagnetic shielding
• 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 33/382 : the electrode extending partially in or entirely through the semiconductor body
• CPC Class Codes: H01L 33/505 : characterised by the shape, e.g. plate or foil
• CPC Class Codes: H01L 33/507 : the elements being in intimate contact with parts other than the semiconductor body or integrated with parts other than the semiconductor body
• CPC Class Codes: H01L 33/58 : Optical field-shaping elements

Abstract

In order to provide light emitting devices which have simple constructions and thus can be fabricated easily, and can stably provide high light emission efficiencies for a long time period, a light emitting device includes an n-type nitride semiconductor layer at a first main surface side of a nitride semiconductor substrate, a p-type nitride semiconductor layer placed more distantly from the nitride semiconductor substrate than the n-type nitride semiconductor layer at the first main surface side and a light emitting layer placed between the n-type nitride semiconductor layer and the p-type nitride semiconductor layer at the first main surface side. The nitride semiconductor substrate has a resistivity of 0.5 Ω·cm or less and the p-type nitride semiconductor layer side is down-mounted so that light is emitted from the second main surface of the nitride semiconductor substrate at the opposite side from the first main surface.

Claims

1. A light emitting apparatus comprising:

a nitride semiconductor substrate;

a n-type nitride semiconductor layer at a first main surface side of said nitride semiconductor substrate;

a p-type nitride semiconductor layer, at said first main surface side, placed more distantly from said nitride semiconductor substrate than said n-type nitride semiconductor layer; and

a light emitting layer, at said first main surface side, placed between said n-type nitride semiconductor layer and said p-type nitride semiconductor layer, wherein

said nitride semiconductor substrate has a resistivity of 0.5 Ω

·

cm or less and said p-type nitride semiconductor layer side is down-mounted so that light is emitted from a second main surface of said nitride semiconductor substrate at the opposite side from said first main surface.

2. The light emitting apparatus according to claim 1, comprising:

a first p-electrode placed discretely over the surface of said p-type nitride semiconductor layer in contact with said p-type nitride semiconductor layer; and

a second p-electrode formed from any one of Ag, Al and Rh which fills the gaps of said first p-electrode and covers said p-type nitride semiconductor layer and said first p-electrode.

3. The light emitting apparatus according to claim 2, wherein

the coverage ratio of said first p-electrode on the surface of said p-type nitride semiconductor layer is within the range of 10% to 40%.

4. The light emitting apparatus according to claim 1, wherein

said light emitting apparatus has an electrostatic withstand voltage of 3000 V or more.

5. The light emitting apparatus according to claim 1, wherein

there is no protection circuit for protecting said light emitting apparatus against transient voltages or static discharge applied between said nitride semiconductor substrate and said down-mounted p-type Al_xGa_1-xN layer side.

6. The light emitting apparatus according to claim 5, wherein

there is no electrical power branch circuit including Zener diodes for addressing said transient voltages or static discharge.

7. The light emitting apparatus according to claim 1, wherein

said light emitting apparatus causes light emission by an applied voltage of equal to or lower than 4 V.

8. The light emitting apparatus according to claim 1, wherein

the thickness of said nitride semiconductor substrate is 50 μ

m or larger.

9. The light emitting apparatus according to claim 1, wherein

an electrode is provided on the second main surface of said nitride semiconductor substrate with an opening ratio of 50% or more.

10. The light emitting apparatus according to claim 1, wherein

the contact area between an electrode provided on said nitride semiconductor substrate and said nitride semiconductor substrate is 0.055 mm² or more.

11. The light emitting apparatus according to claim [1] 10, wherein

the cross sectional area of a bonding wire connecting said electrode and a lead frame is 0.002 mm² or more.

12. The light emitting apparatus according to claim 11, wherein

the cross sectional area of a bonding wire connecting said electrode and a lead frame is 0.07 mm² or more.

13. The light emitting apparatus according to claim 10, wherein

said electrode is placed at two or more corners of said nitride semiconductor substrate and the sum of the contact areas between said electrodes and said nitride semiconductor substrate is 0.055 mm² or more, and the sum of the cross sectional areas of bonding wires connecting said electrodes placed at said corners and a lead frame is 0.002 mm² or more.

14. The light emitting apparatus according to claim 13, wherein

the sum of the cross sectional areas of bonding wires connecting said electrodes placed at said corners and the lead frame is 0.07 mm or more.

15. The light emitting apparatus according to claim 1, wherein

the light emitting area in the second main surface of said nitride semiconductor substrate is 0.25 mm² or more.

16. The light emitting apparatus according to claim 1, wherein

the light emitting area of the second main surface of said nitride semiconductor substrate has a size equal to or larger than 1 mm×

1 mm.

17. The light emitting apparatus according to claim 16, wherein

the light emitting area of the second main surface of said nitride semiconductor substrate has a size equal to or larger than 3 mm×

3 mm.

18. The light emitting apparatus according to claim 16, wherein

the light emitting area of the second main surface of said nitride semiconductor substrate has a size equal to or larger than 5 mm×

5 mm.

19. The light emitting apparatus according to claim 1, which is constituted to have a heat resistance of 30°

C./W or less.

20. The light emitting apparatus according to claim 1, wherein

the temperature of the portion at which the temperature increases most largely in continuous light emitting conditions is 150°

C. or lower.

21. The light emitting apparatus according to claim 1, wherein

the thickness of said n-type nitride semiconductor layer is 3 μ

m or less.

22. The light emitting apparatus according to claim 1, wherein

the area of the second main surface of said nitride semiconductor substrate which is not coated with said electrode has been non-mirror-surface finished.

23. The light emitting apparatus according to claim 22, wherein

said surface which has been non-mirror-surface finished is a surface which has been non-mirror-surface finished by using potassium hydroxide (KOH) solution, sodium hydroxide (NaOH) solution, or ammonia (NH₃) solution or other alkali solutions.

24. The light emitting apparatus according to claim 22, wherein

said surface which has been non-mirror-surface finished is a surface which has been non-mirror-surface finished by using at least one of sulfuric acid (H₂SO₄) solution, hydrochloric acid (HCl) solution, phosphoric acid (H₂PO₄) solution, hydrofluoric acid (HF) solution or other acid solutions.

25. The light emitting apparatus according to claim 22, wherein

said surface which has been non-mirror-surface finished is a surface which has been non-mirror-surface finished by using reactive ion etching (RIE).

26. The light emitting apparatus according to claim 1, wherein

said electrode provided on said p-type nitride semiconductor layer is formed from a material with a reflectivity of 0.5 or more.

27. The light emitting apparatus according to claim 1, wherein

a fluorescence member is placed to cover the second main surface of said nitride semiconductor substrate.

28. The light emitting apparatus according to claim 1, wherein

a fluorescence plate is placed opposite to the second main surface of said nitride semiconductor substrate apart from said nitride semiconductor substrate.

29. The light emitting apparatus according to claim 28, wherein

the surface of said fluorescence plate which faces the second main surface of said nitride semiconductor substrate has been subjected to a projection/depression forming process.

30. The light emitting apparatus according to claim 1, wherein

said nitride semiconductor substrate include at least one of impurities and defects which generate fluorescence.

31. A light emitting apparatus comprising:

two or more light emitting apparatuses according to claim 1 and these light emitting apparatuses are connected in serial or parallel.

32. The light emitting apparatus comprising said light emitting apparatuses according to claim 1 and a power supply circuit for causing the light emitting apparatuses to generate light emission, wherein in said power supply circuit, two or more parallel sections in which two or more said light emitting apparatuses are connected in parallel are connected in serial.

33. A light emitting apparatus comprising:

a GaN substrate which is a nitride semiconductor substrate;

an n-type Al_xGa_1-xN layer (x is in the range of from 0 to

     1) which is an n-type nitride semiconductor layer at a first main surface side of said GaN substrate;

a p-type Al_xGa_1-xN layer (x is within the range of from 0 to

     1), at said first main surface side, placed more distantly from said GaN substrate than said n-type Al_xGa_1-xN layer; and

a light emitting layer, at said first main surface side, placed between said n-type Al_xGa_1-xN layer and said p-type Al_xGa_1-xN layer, wherein

said GaN substrate has a dislocation density of 10⁸/cm² or less, and said p-type Al_xGa_1-xN layer side is down-mounted so that light is emitted from the second main surface of said GaN substrate at the opposite side from the first main surface.

34. The light emitting apparatus according to claim 33, wherein

said GaN substrate has been n-typed by oxygen doping, the oxygen concentration is within the range of oxygen atoms 1E17/cm³ to 2E19/cm³ and the thickness of said GaN substrate is from 100 μ

m to 600 μ

m.

35. The light emitting apparatus according to claim 33, wherein

said oxygen concentration is within the range of oxygen atoms 5E18/cm³ to 2E19/cm³ and the thickness of said GaN substrate is within the range of from 200 μ

m to 400 μ

m and the both sides of the rectangular surface which emits light at said main surface is equal to or smaller than 10 mm.

36. The light emitting apparatus according to claim 33, wherein

said oxygen concentration is within the range of oxygen atoms 3E18/cm³ to 5E18/cm³ and the thickness of said GaN substrate is within the range of from 400 μ

m to 600 μ

m and the both sides of the rectangular surface which emits light at said second main surface is equal to or smaller than 3 mm.

37. The light emitting apparatus according to claim 33, wherein

said oxygen concentration is within the range of oxygen atoms 5E18/cm³ to 5E19/cm³ and the thickness of said GaN substrate is within the range of from 100 μ

m to 200 μ

m and the both sides of the rectangular surface which emits light at said second main surface is equal to or smaller than 3 mm.

38. The light emitting apparatus according to claim 33, wherein

dislocation bundles (61) are distributed on the first main surface of said GaN substrate with a density of 4E6/cm² or less on average and said dislocation bundles are generated by discretely concentrating dislocations, which have been unavoidably generated during formation of the GaN substrate, in a string shape to distribute them along the substrate thick-wise direction in order to increase the crystalinity of most area of said GaN substrate.

39. The light emitting apparatus according to claim 33, wherein

said dislocation bundles are distributed on said first main surface with a density of 4E2/cm² or less on average and the both sides of the rectangular surface which emits light at said second main surface is within the range of 200 μ

m to 400 μ

m.

40. The light emitting apparatus according to claim 33, wherein

between said GaN substrate and said n-type Al_xGa_1-xN layer (x is within the range of from 0 to 1), an n-type AlGaN buffer layer is placed in contact with said GaN substrate and an n-type GaN buffer layer is placed in contact with the n-type AlGaN buffer layer, and said n-type Al_xGa_1-xN layer (x is within the range of from 0 to 1) is placed in contact with the n-type GaN buffer layer.

41. The light emitting apparatus according to claim 40, wherein

said GaN substrate includes areas with an off-angle of 0.10°

or less and areas with an off-angle of 1.0°

or greater.

42. The light emitting apparatus according to claim 40, wherein

dislocation bundles are distributed in said GaN substrate and said dislocation bundles are not transferred to said n-type Al_xGa_1-xN layer (x is within the range of 0 to 1) placed in contact with said GaN buffer layer.

43. The light emitting apparatus according to claim 33 comprising a p-type GaN buffer layer placed at the down side in contact with said p-type Al_xGa_1-xN layer (x is within the range of from 0 to 1) and a p-type InGaN contact layer placed in contact with the p-type GaN buffer layer.

44. The light emitting apparatus according to claim 43, wherein

the Mg concentration of said p-type InGaN contact layer is within the range of Mg atoms 1E18/cm³ to 1E21/cm³.

45. The light emitting apparatus according to claim 43 comprising a p-electrode layer formed from any one of Ag, Al and Rh in contact with said p-type InGaN contact layer.

46. The light emitting apparatus according to claim 33, wherein

said GaN substrate includes plate-shape crystal inversion domains extending continuously in a plane shape in the thick-wise direction and a single direction within the GaN substrate surface, the plate-shape crystal inversion domains within the GaN substrate surface and plate-shape crystal inversion domains propagated to said n-type and p-type nitride semiconductor layers formed on said GaN substrate are removed from said p-type nitride semiconductor layers side through said n-type nitride semiconductor layers to a position inside of said GaN substrate, and in contact with the left p-type nitride semiconductor layers, p-electrodes are provided on the respective p-type nitride semiconductor layers.

47. The light emitting apparatus according to claim 46, wherein

said plate-shape crystal inversion domains are removed to a position inside of said GaN substrate by KOH solution.

48. A light emitting apparatus comprising:

a conductive AlN substrate which is a nitride semiconductor substrate;

an n-type Al_xGa_1-xN layer (x is in the range of from 0 to

     1) which is an n-type nitride semiconductor layer at a first main surface side of said AlN substrate;

a p-type Al_xGa_1-xN layer (x is in the range of from 0 to

     1), at said first main surface side, placed more distantly from said AlN substrate than said n-type Al_xGa_1-xN layer; and

a light emitting layer, at said first main surface side, placed between said n-type Al_xGa_1-xN layer and said p-type Al_xGa_1-xN layer, wherein

said AlN substrate has a heat conductivity of 100 W/(m·

K) or higher, and said p-type Al_xGa_1-xN layer side is down-mounted so that light is emitted from a second main surface of said AlN substrate at the opposite side from said first main surface.