Crystal producing apparatus, crystal producing method, substrate producing method, gallium nitride crystal, and gallium nitride substrate

• US 20080081015A1
• Filed: 10/01/2007
• Published: 04/03/2008
• Est. Priority Date: 10/02/2006
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Sarayama, Seiji, Iwata, Hirokazu
• Granted Patent: US 8,337,798 B2
• Time in Patent Office: Days
• US Class Current: 423/409
• CPC Class Codes: C30B 17/00 Single-crystal growth onto a seed which remains in the melt during growth, e.g. Nacken-Kyropoulos method C30B15/00 takes precedence
• CPC Class Codes: C30B 23/025 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 29/403 AIII-nitrides
• 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 21/20 Deposition of semiconductor materials on a substrate, e.g. epitaxial growth solid phase epitaxy
• CPC Class Codes: H01L 29/2003 Nitride compounds
• CPC Class Codes: Y10T 117/10 Apparatus

Abstract

A crystal producing apparatus includes a crystal forming unit and a crystal growing unit. The crystal forming unit forms a first gallium nitride (GaN) crystal by supplying nitride gas into melt mixture containing metal sodium (Na) and metal gallium (Ga). The first GaN crystal is sliced and polished to form GaN wafers. The crystal growing unit grows a second GaN crystal on a substrate formed by using a GaN wafer, by the hydride vapor phase epitaxy method, thus producing a bulked GaN crystal.

Claims

1. An apparatus that produces a group-III nitride crystal, the apparatus comprising a crystal growing unit that grows by vapor phase epitaxy method a second group-III nitride crystal on a first group-III nitride crystal that is formed by flux method.

2. The apparatus according to claim 1, further comprising a crystal forming unit that forms the first group-III nitride crystal by supplying nitrogen source gas into melt mixture containing alkali metal and group-III metal.

3. The apparatus according to claim 2, wherein

the crystal forming unit forms the first group-III nitride crystal at a first crystal-growth speed, and

the crystal growing unit grows the second group-III nitride crystal at a second crystal-growth speed that is faster than the first crystal-growth speed.

4. The apparatus according to claim 2, wherein the crystal forming unit forms the first group-III nitride crystal from a seed crystal.

5. A method of producing a group-III nitride crystal, the method comprising growing a second group-III nitride crystal by vapor phase epitaxy method on a first group-III nitride crystal that is formed by flux method.

6. The method according to claim 5, further comprising forming the first group-III nitride crystal by supplying nitrogen source gas into melt mixture containing alkali metal and group-III metal.

7. The method according to claim 6, wherein

the forming includes forming the first group-III nitride crystal at a first crystal-growth speed, and

the growing includes growing the second group-III nitride crystal at a second crystal-growth speed that is faster than the first crystal-growth speed.

8. The method according to claim 6, wherein the forming includes forming the first group-III nitride crystal from a seed crystal.

9. The method according to claim 5, wherein the first group-III nitride crystal is in a plate shape.

10. The method according to claim 9, wherein a principal surface of the first group-III nitride crystal is one of an m-plane, an a-plane, and a c-plane.

11. The method according to claim 5, further comprising slicing the first group-III nitride crystal before performing the growing.

12. The method according to claim 11, wherein the slicing includes slicing the first group-III nitride crystal in such a manner that a principal surface of the first group-III nitride crystal is one of an m-plane, an a-plane, and a c-plane.

13. The method according to claim 9, wherein the first group-III nitride crystal is capable of being reused.

14. The method according to claim 11, wherein the first group-III nitride crystal is capable of being reused.

15. The method according to claim 5, wherein the first group-III nitride crystal is in a columnar shape, in which a length in a c-axis direction is longer than a length in an a-axis direction.

16. The method according to claim 5, wherein the first group-III nitride crystal and the second group-III nitride crystal are gallium nitride crystals.

17. A methof of producing a substrate, the method comprising:

manufactruing a bulk of group-III nitride crystal by using the method according to claim 5; and

manufacturing a group-III nitride substrate by slicing the bulked group-III nitride crystal.

18. The method according to claim 17, wherein the slicing includes slicing the bulked group-III nitride crystal in such a manner that a principal surface of the bulked group-III nitride crystal is one of an m-plane, an a-plane, and a c-plane.

19. The method according to claim 17, wherein the bulked group-III nitride crystal is a gallium nitride crystal.

21. The gallium nitride crystal according to claim 19, wherein the first gallium nitride crystal is enclosed by the second gallium nitride crystal.

20. A gallium nitride crystal in bulks comprising:

a first gallium nitride crystal formed by flux method; and

a second gallium nitride crystal grown on the first gallium nitride crystal.

22. The gallium nitride crystal according to claim 20, wherein the gallium nitride crystal is sliced to form a gallium nitride substrate.

23. The gallium nitride crystal according to claim 22, wherein the gallium nitride crystal is sliced in such a manner that a principal surface of the gallium nitride crystal is one of an m-plane, an a-plane, and a c-plane.