Composite substrate for formation of light-emitting device, light-emitting diode device and manufacturing method thereof

1. A composite substrate for formation of a light-emitting device, comprising:

a tight-converting material substrate that radiates at least a part of incident light as light different in wavelength through a surface opposite an incident surface, wherein said light-converting material substrate has a texture comprising two or more oxide phases continuously and three-dimensionally entangled with each other, said two or more oxide phases including an Al 2 O 3 phase and at least one fluorescence-emitting oxide phase, and

at least two or more Al-containing nitride layers formed on said light-converting material substrate, wherein said nitride layers have a first layer of an Al-containing nitride layer formed on the light-converting material substrate and a second layer of AlN having a dislocation density of 1×10 12 /cm 2 or less, said first layer having a thickness of from 0.5 to 5 μm and said second layer having a thickness of from 2 to 9 μm,

wherein said Al-containing nitride layers are layers to ensure a high-quality nitride-based light-emitting diode, optionally, with an intermediate layer therebetween, to be formed thereon.

2. The composite substrate as claimed in claim 1 , wherein each of said first layer and said second layer forms a uniform continuous layer on said two or more oxide phases of said light-converting material substrate to extend across all phases and contains substantially no voids.

3. The composite substrate as claimed in claim 1 , wherein said second layer has a surface roughness (root-mean-square roughness, RMS of 5 nm or less.

4. The composite substrate as claimed in claim 1 , wherein the fluorescence-emitting oxide phase of said light-convening material substrate is Y 3 Al 5 O 12 :Ce phase.

5. The composite substrate claimed in claim 4 , wherein (0001) of said Al 2 O 3 crystal and (111) of said Y 3 Al 5 O 12 :Ce crystal serve as principal surfaces of said light-converting material substrate.

6. The composite substrate as claimed in claim 1 , wherein the Al-containing nitride layer of said first layer and the AlN layer of said second layer are grown as crystals by the MOCVD method on said light-convening material substrate.

7. The composite substrate as claimed, in claim 1 , wherein the Al-containing nitride layer of said first layer is AlN.

8. A light-emitting diode device comprising a semiconductor light-emitting layer formed on said composite substrate of claim 1 , wherein said light-emitting diode device radiates light after wavelength conversion of at least a part of light from the semiconductor light-emitting light through said composite substrate to form a light-emitting device.

9. A light-emitting diode device comprising:

the composite substrate claimed in claim 4 ; and

a semiconductor light-emitting layer capable of emitting blue light on said composite substrate,

wherein said light-emitting diode device radiates light after wavelength conversion of a part of light from said semiconductor light-emitting light, together with light from said semiconductor light-emitting layer, through said composite substrate.

10. A method of producing said composite substrate of claim 1 , comprising:

a first step of subjecting a light-converting material substrate having a texture comprising two or more oxide phases continuously and three-dimensionally entangled with each other, said two or more phases including an Al 3 O 3 phase and at least one fluorescence-emitting oxide phase to radiate at least a part of incident light as light different in wavelength through the surface opposite the incident surface to a heat treatment at 1,000 to 1,300° C. in a mixed gas atmosphere of an H 2 gas, an N 2 gas and an NH 3 gas,

a second step of supplying at least an H 2 gas, an N 2 gas, an NH 3 gas and an Al-containing organic metal compound gas on said light-converting material substrate at a temperature of 400 to 1,300° C. to form a first layer of an Al-containing nitride layer having a thickness of from 0.5 to 5 μm, and

a third step of supplying a mixed gas of an H 2 gas, an N 2 gas, an NH 3 gas and an Al-containing organic metal compound gas on said first layer at 1,350 to 1,480° C. to form a second layer of AlN having a thickness of from 2 to 9 μm.

11. The method as claimed in claim 10 , wherein said first step, said second step and said third step are performed by the MOCVD method.

12. The method as claimed in claim 10 , wherein a molar ratio between N in the NH 3 gas and Al in the Al-containing organic metal compound was in said third step is smaller than a molar ratio between N in the NH 3 gas and Al in the Al-containing organic metal compound gas in said second step.

13. The method as claimed in claim 10 , wherein a heat treatment time period in said first step is from 10 to 90 minutes.

14. The method as claimed in claim 10 , wherein said Al-containing nitride layer is AlN.

15. The composite substrate as claimed in claim 2 , wherein said second layer has a surface roughness (root-mean-square roughness, RMS) of 5 nm or less.

16. The composite substrate as claimed in claim 1 , wherein film thickness of said second layer is from 4 μm to 9 μm.

17. The method as claimed in claim 11 , wherein a molar ratio between N in the NH 3 gas and Al in the Al-containing organic metal compound as in said third step is smaller than a molar ratio between N in the NH 3 gas and Al in the Al-containing organic metal compound gas in said second step.

18. The composite substrate as claimed in claim 1 , wherein said second layer of AlN has a dislocation density of 1×10 9 /cm 2 less.

19. The method according to claim 10 , wherein said first layer of an Al containing nitride layer is formed at a temperature of 1,000 to 1,300° C.