Group III nitride bulk crystals and fabrication method

Patent metadata

Field	Value
Publication number	US-9834863-B2
Application number	US-201514598982-A
Country	US
Kind code	B2
Filing date	Jan 16, 2015
Priority date	Apr 7, 2006
Publication date	Dec 5, 2017
Grant date	Dec 5, 2017

Abstract

Bulk crystal of group III nitride having thickness greater than 1 mm with improved crystal quality, reduced lattice bowing and/or reduced crack density and methods of making. Bulk crystal has a seed crystal, a first crystalline portion grown on the first side of the seed crystal and a second crystalline portion grown on the second side of the seed crystal. Either or both crystalline portions have an electron concentration and/or an oxygen concentration similar to the seed crystal.
The bulk crystal can have an additional seed crystal, with common faces (e.g. same polarity, same crystal plane) of seed crystals joined so that a first crystalline part grows on the first face of the first seed crystal and a second crystalline part grows on the first face of the second seed crystal. Each crystalline part's electron concentration and/or oxygen concentration may be similar to its corresponding seed crystal.

First claim

What is claimed is:

1. A bulk crystal of group III nitride having a composition of Ga x Al y In 1-x-y N (0≦x≦1, 0≦x+y≦1) and a thickness greater than 1 millimeter wherein the bulk crystal has at least three portions,
(a) a first portion comprising a seed crystal containing a donor dopant other than oxygen and having a first major face and a second major face, the first major face having an electron concentration, N 1seed , and the second major face having an electron concentration N 2seed ;
(b) a second portion on the first major face of the seed crystal and comprising a first crystalline region, wherein the first crystalline region has an electron concentration, N 1st-xtal ,
(c) a third portion on the second major face of the seed crystal and comprising a second crystalline region, wherein said second crystalline region has an electron concentration N 2nd-xtal , and
(d) wherein the electron concentration of the seed crystal, the first crystalline region, and the second crystalline region satisfy the following relationship:
0.1<N 1st-xtal /N 1seed <10 and/or 0.1<N 2nd-xtal /N 2seed <10.

2. A bulk crystal according to claim 1 wherein the electron concentration of the seed crystal, the first crystalline region, and the second crystalline region satisfy the following relationship:
0.5<N 1st-xtal /N 1seed <5 and/or 0.5<N 2nd-xtal /N 2seed <5.

3. A bulk crystal according to claim 1 wherein the seed crystal is a single crystal of said Ga x Al y In 1-x-y N, the electron concentration of said first crystalline region satisfies said relationship, and the electron concentration of the second crystalline region does not satisfy said relationship.

4. A bulk crystal according to claim 1 wherein the seed crystal is a composite crystal of said Ga x Al y In 1-x-y N, and wherein the composite crystal comprises a first seed crystal piece of said Ga x Al y In 1-x-y N and a separate, second seed crystal piece of said Ga x Al y In 1-x-y N affixed to a major face of the first seed crystal piece.

5. A bulk crystal according to claim 4 wherein the electron concentration of the first crystalline region satisfies said relationship and wherein the electron concentration of the second crystalline region also satisfies said relationship.

6. A bulk crystal according to claim 4 wherein the first major face of the seed crystal is N-polar and the second major face of the seed crystal is N-polar.

7. A bulk crystal according to claim 1 wherein said first crystalline region of the bulk crystal has a full width half maximum of an x-ray rocking curve less than a full width half maximum of an x-ray rocking curve of the seed crystal.

8. A bulk crystal according to claim 1 wherein the first crystalline region has a radius of curvature of crystal lattice, the first major face of the seed crystal has a radius of curvature of crystal lattice, and an absolute value of the radius of curvature of the crystal lattice of the first crystalline region is greater than the absolute value of the radius of curvature of the crystal lattice of the first major face of the seed crystal.

9. A bulk crystal according to claim 8 wherein the absolute value of the radius of curvature of the crystal lattice of the first crystalline region exceeds 10 m.

10. A bulk crystal according to claim 1 wherein the first crystalline region has a major face having a crack density less than 10 cm −2 .

11. A bulk crystal according to claim 1 wherein the group III nitride is GaN.

12. A bulk crystal according to claim 1 , wherein at least one of the first crystalline region and the second crystalline region of the bulk crystal has better crystal quality, better defect density, and/or better crack density than a comparative bulk crystal of equal thickness formed by a method identical to a method of forming the bulk crystal above except that electron concentration of new growth is not matched to electron concentration of the seed crystal.

13. A method of fabricating a bulk crystal of group III nitride comprising;
(a) preparing a seed crystal of group III nitride, wherein the seed crystal has a donor dopant other than oxygen and a first major face having an electron concentration of N 1seed and a second major face having an electron concentration of N 2seed ;
(b) simultaneously growing a first crystalline portion of group III nitride on the first major face of the seed crystal and a second crystalline portion of group III nitride on the second major face of the second seed crystal wherein group III nitride growth conditions are selected so that the electron concentration of the first crystalline portion (N 1st-xtal ) and the electron concentration of the second crystalline portion (N 2nd-xtal ) satisfy the following relationship:
0.1<N 1st-xtal /N 1seed <10 and/or 0.1<N 2nd-xtal /N 2seed <10.

14. A method according to claim 13 wherein the reaction conditions are selected so that the electron concentration of the first crystalline portion (N 1st-xtal ) and the electron concentration of the second crystalline portion (N 2nd-xtal ) satisfy the following relationship:
0.5<N 1st-xtal /N 1seed <5 and/or 0.5<N 2nd-xtal /N 2seed <5.

15. A method according to claim 13 wherein the seed crystal is a single crystal of said group III nitride and the operating conditions are selected so that the electron concentration satisfies said relationship and the electron concentration of the second crystalline portion does not satisfy said relationship.

16. A method according to claim 13 wherein the seed crystal is a single crystal of said group III nitride, and the operating conditions are selected so that the electron concentration of the first crystalline portion satisfies said relationship and the electron concentration of the second crystalline portion additionally satisfies said relationship.

17. A method according to claim 13 wherein the seed crystal is a composite crystal comprising a first seed crystal piece of said group III nitride and a separate, second seed crystal piece of said group III nitride affixed to a major face of the first seed crystal piece.

18. A method according to claim 17 wherein the composite crystal has a first exposed major face and a second exposed major face and wherein each of the first and second exposed major faces are N-polar.

19. A method according to claim 17 wherein the operating conditions are selected so that the electron concentration of the first crystalline portion satisfies said relationship and wherein the electron concentration of the second crystalline portion also satisfies said relationship.

20. A method according to claim 13 wherein the bulk crystal is grown in supercritical ammonia.

21. A method according to claim 13 wherein the seed crystal is grown in supercritical ammonia.

22. A method according to claim 13 wherein the group III nitride is GaN.

23. A bulk crystal formed by a method of claim 13 wherein the bulk crystal has a first major face and a second major face, and the absolute value of curvature radius of crystal lattice measured on the first major face, the second major face, or both the first major face and the second major face is greater than that of the original seed crystal.

24. A method according to claim 13 wherein the seed crystal is grown by hydride vapor phase epitaxy.

25. A method according to claim 13 in which the donor dopant is selected from silicon, carbon, germanium, sulfur, and selenium.

26. A m

Assignees

• Sixpoint Mat Inc
• Seoul Semiconductor Co Ltd

Inventors

• Hashimoto Tadao
• Letts Edward

Classifications

• C30B7/105

  using ammonia as solvent, i.e. ammonothermal processes · CPC title

• C30B29/403 Primary

  AIII-nitrides · CPC title