GALLIUM NITRIDE SELF-SUPPORTED SUBSTRATE, LIGHT-EMITTING DEVICE AND MANUFACTURING METHOD THEREFOR

• US 20150144956A1
• Filed: 09/29/2014
• Published: 05/28/2015
• Est. Priority Date: 05/31/2013
• Status: Active Grant

• Current Assignee: NGK Insulators Limited
• Original Assignee: NGK Insulators Limited
• Inventors: YOSHIKAWA, Jun, IMAI, Katsuhiro, SUGIYAMA, Tomohiko, SATO, Kei, WATANABE, Morimichi, NANATAKI, Tsutomu, YOSHINO, Takashi, TAKEUCHI, Yukihisa
• Granted Patent: US 9,312,446 B2
• Time in Patent Office: Days
• US Class Current: 257/76
• CPC Class Codes: C30B 19/02 using molten solvents, e.g. flux
• CPC Class Codes: C30B 19/12 characterised by the substrate
• CPC Class Codes: C30B 25/18 characterised by the substrate
• CPC Class Codes: C30B 25/20 the substrate being of the same materials as the epitaxial layer
• CPC Class Codes: C30B 28/04 from liquids
• CPC Class Codes: C30B 29/406 Gallium nitride
• CPC Class Codes: C30B 29/605 Products containing multiple oriented crystallites, e.g. columnar crystallites
• CPC Class Codes: C30B 9/00 Single-crystal growth from melt solutions using molten solvents by normal or gradient freezing C30B11/00; by zone-melting C30B13/00; by crystal pulling C30B15/00; on immersed seed crystal C30B17/00; by liquid phase epitaxial growth C30B19/00; under a protective fluid C30B27/00
• CPC Class Codes: C30B 9/12 Salt solvents, e.g. flux growth
• CPC Class Codes: H01L 33/0025 comprising only AIIIBV compounds
• CPC Class Codes: H01L 33/0075 comprising nitride compounds
• CPC Class Codes: H01L 33/06 within the light emitting region, e.g. quantum confinement structure or tunnel barrier
• CPC Class Codes: H01L 33/16 with a particular crystal structure or orientation, e.g. polycrystalline, amorphous or porous
• CPC Class Codes: H01L 33/18 within the light emitting region
• CPC Class Codes: H01L 33/32 containing nitrogen

Abstract

Provided is a self-supporting gallium nitride substrate useful as an alternative material for a gallium nitride single crystal substrate, which is inexpensive and also suitable for having a large area. This substrate is composed of a plate composed of gallium nitride-based single crystal grains, wherein the plate has a single crystal structure in the approximately normal direction. This substrate can be manufactured by a method comprising providing an oriented polycrystalline sintered body; forming a seed crystal layer composed of gallium nitride on the sintered body so that the seed crystal layer has crystal orientation mostly in conformity with the crystal orientation of the sintered body; forming a layer with a thickness of 20 μm or greater composed of gallium nitride-based crystals on the seed crystal layer so that the layer has crystal orientation mostly in conformity with crystal orientation of the seed crystal layer; and removing the sintered body.

Claims

1. A self-supporting gallium nitride substrate composed of a plate composed of a plurality of gallium nitride-based single crystal grains, wherein the plate has a single crystal structure in an approximately normal direction.

2. The self-supporting gallium nitride substrate according to claim 1, wherein a cross-sectional average diameter of the gallium nitride-based single crystal grains at an outermost surface of the substrate is 0.3 μ

m or greater.

3. The self-supporting gallium nitride substrate according to claim 2, wherein the cross-sectional average diameter is 3 μ

m or greater.

4. The self-supporting gallium nitride substrate according to claim 2, wherein the cross-sectional average diameter is 20 μ

m or greater.

5. The self-supporting gallium nitride substrate according to claim 1, having a thickness of 20 μ

m or greater.

6. The self-supporting gallium nitride substrate according to claim 1, having a diameter of 100 mm or greater.

7. The self-supporting gallium nitride substrate according to claim 1, wherein the gallium nitride-based single crystal grains have crystal orientation that is mostly aligned in the approximately normal direction.

8. The self-supporting gallium nitride substrate according to claim 1, wherein the gallium nitride-based single crystal grains are doped with an n-type dopant or a p-type dopant.

9. The self-supporting gallium nitride substrate according to claim 1, wherein the gallium nitride-based single crystal grains are free from a dopant.

10. The self-supporting gallium nitride substrate according to claim 1, wherein the gallium nitride-based single crystal grains are made of a mixed crystal.

11. The self-supporting gallium nitride substrate according to claim 1, wherein the gallium nitride-based single crystal grains exposed at a top surface of the self-supporting gallium nitride substrate connect to a bottom surface of the self-supporting gallium nitride substrate without intervention of a grain boundary.

12. The self-supporting gallium nitride substrate according to claim 1, wherein a ratio D_T/D_B, which is a ratio of a cross-sectional average diameter D_T at an outermost surface of the gallium nitride-based single crystal grains exposed at a top surface of the self-supporting gallium nitride substrate to a cross-sectional average diameter D_B at an outermost surface of the gallium nitride-based single crystal grains exposed at a bottom surface of the self-supporting gallium nitride substrate, is 1.0 or greater.

13. The self-supporting gallium nitride substrate according to claim 1, wherein an aspect ratio T/D_T, which is defined as a ratio of a thickness T of the self-supporting gallium nitride substrate to a cross-sectional average diameter D_T at an outermost surface of the gallium nitride-based single crystal grains exposed at a top surface of the self-supporting gallium nitride substrate, is 0.7 or greater.

14. A light emitting device comprising:

the self-supporting gallium nitride substrate according to claim 1; and

a light emitting functional layer formed on the substrate, wherein the light emitting functional layer has at least one layer composed of a plurality of semiconductor single crystal grains, wherein the at least one layer has a single crystal structure in an approximately normal direction.

15. The self-supporting light emitting device according to claim 14, wherein a cross-sectional average diameter of the semiconductor single crystal grains at an outermost surface of the light emitting functional layer is 0.3 μ

m or greater.

16. The light emitting device according to claim 15, wherein the cross-sectional average diameter is 3 μ

m or greater.

17. The light emitting device according to claim 14, wherein the semiconductor single crystal grains have a structure in which grains are grown mostly in conformity with crystal orientation of the self-supporting gallium nitride substrate.

18. The light emitting device according to claim 14, wherein the light emitting functional layer is composed of a gallium nitride-based material.

24. A method for manufacturing a light emitting device, comprising the steps of:

providing the self-supporting gallium nitride substrate of claim 1; and

forming on the self-supporting gallium nitride substrate at least one layer composed of a plurality of semiconductor single crystal grains, wherein the at least one layer has a single crystal structure in an approximately normal direction, so that the at least one layer has crystal orientation mostly in conformity with crystal orientation of the gallium nitride substrate, thereby providing a light emitting functional layer.

25. The method according to claim 24, wherein the light emitting functional layer is composed of a gallium nitride-based material.

19. A method for manufacturing a self-supporting gallium nitride substrate, comprising the steps of:

providing an oriented polycrystalline sintered body;

forming a seed crystal layer composed of gallium nitride on the oriented polycrystalline sintered body so that the seed crystal layer has crystal orientation mostly in conformity with crystal orientation of the oriented polycrystalline sintered body;

forming a layer with a thickness of 20 μ

m or greater composed of gallium nitride-based crystals on the seed crystal layer so that the layer has crystal orientation mostly in conformity with crystal orientation of the seed crystal layer; and

removing the oriented polycrystalline sintered body to obtain the self-supporting gallium nitride substrate.

20. The method according to claim 19, wherein the oriented polycrystalline sintered body is an oriented polycrystalline alumina sintered body.

21. The method according to claim 19, wherein an average grain diameter of grains constituting the oriented polycrystalline sintered body on a plate surface is 0.3 to 1000 μ

m.

22. The method according to claim 19, wherein formation of the layer composed of the gallium nitride-based crystals is performed by Na flux method.

23. The method according to claim 19, wherein the oriented polycrystalline sintered body is transparent or translucent.