Aluminum nitride single crystals having large crystal augmentation parameters

Patent metadata

Field	Value
Publication number	US-12227873-B2
Application number	US-202016991278-A
Country	US
Kind code	B2
Filing date	Aug 12, 2020
Priority date	Aug 15, 2019
Publication date	Feb 18, 2025
Grant date	Feb 18, 2025

Abstract

In various embodiments, aluminum nitride single crystals have large crystal augmentation parameters and may therefore be suitable for the fabrication of numerous, large single-crystal aluminum nitride substrates having high crystalline quality. The aluminum nitride single crystals may have large boule masses and volumes.

First claim

The invention claimed is:

1. An AlN single crystal having a diameter that increases, along at least a portion of a length of the AlN single crystal, from a minimum diameter, ranging from 50 mm to 100 mm, to a maximum diameter, the AlN single crystal having a crystal augmentation parameter (CAP), in mm, greater than 20, the CAP being defined by:

CAP
=

A
E

-

A
S

L
E

=

π

4
×

L
E

⁢

(

d
E
2

-

d
S
2

)

wherein A E , in mm 2 , is the cross-sectional area of the AlN single crystal at the maximum diameter, d E is the maximum diameter of the AlN single crystal in mm, A S , in mm 2 , is the cross-sectional area of the AlN single crystal at the minimum diameter, d S is the minimum diameter in mm, and L E is an expansion length, in mm, of the at least a portion of the AlN single crystal along which the diameter increases from the minimum diameter to the maximum diameter.

2. The AlN single crystal of claim 1 , wherein the CAP is greater than 500.

3. The AlN single crystal of claim 1 , wherein the CAP is greater than 1000.

4. The AlN single crystal of claim 1 , wherein the CAP is less than 2000.

5. The AlN single crystal of claim 1 , wherein a ratio of a total length of the AlN single crystal, in mm, to the maximum diameter, in mm, ranges from approximately 0.3 to approximately 0.6.

6. The AlN single crystal of claim 1 , wherein a ratio of the expansion length of the AlN single crystal, in mm, to the maximum diameter, in mm, ranges from approximately 0.002 to approximately 0.02.

7. The AlN single crystal of claim 1 , wherein a ratio of the expansion length of the AlN single crystal, in mm, to the maximum diameter, in mm, ranges from approximately 0.08 to approximately 0.5.

8. The AlN single crystal of claim 1 , wherein (a) a first region of the AlN single crystal is shaped as a frustum, a maximum diameter of the frustum corresponding to the maximum diameter of the AlN single crystal and the minimum diameter of the frustum corresponding to the minimum diameter of the AlN single crystal, and (b) a second region of the AlN single crystal is shaped as a dome or cone extending from the first region, a maximum diameter of the dome or cone corresponding to the maximum diameter of the AlN single crystal.

9. The AlN single crystal of claim 1 , wherein (a) a first region of the AlN single crystal is shaped as a frustum, a maximum diameter of the frustum corresponding to the maximum diameter of the AlN single crystal and the minimum diameter of the frustum corresponding to the minimum diameter of the AlN single crystal, (b) a second region of the AlN single crystal is shaped as a cylinder extending from the first region and having a diameter corresponding to the maximum diameter of the AlN single crystal, and (c) a third region of the AlN single crystal is shaped as a dome or cone extending from the second region, a maximum diameter of the dome or cone corresponding to the maximum diameter of the AlN single crystal.

10. The AlN single crystal of claim 1 , wherein a density of threading edge dislocations in the AlN single crystal is less than approximately 1×10 4 cm −2 .

11. The AlN single crystal of claim 1 , wherein a density of threading screw dislocations in the AlN single crystal is less than approximately 10 cm −2 .

12. The AlN single crystal of claim 1 , wherein the AlN single crystal exhibits an x-ray rocking curve having a full width at half maximum value less than 50 arcsec.

13. The AlN single crystal of claim 1 , wherein the AlN single crystal has an Urbach energy ranging from approximately 0.2 eV to approximately 1.8 eV within an incident photon energy range of 5.85 eV to 6.0 eV, the Urbach energy E U being defined by:

ln
⁢

⁢
α

=

ln
⁢

⁢

α
0

+

(

hv

E
U

)

wherein α is an absorption coefficient of the AlN single crystal at an incident photon energy hv, and α 0 is a constant corresponding to the absorption coefficient at zero photon energy.

14. The AlN single crystal of claim 1 , wherein the AlN single crystal has an ultraviolet (UV) absorption coefficient of less than 10 cm −1 for an entire wavelength range of 220 nm to 280 nm.

15. The AlN single crystal of claim 14 , wherein the UV absorption coefficient is no less than approximately 5 cm −1 for the entire wavelength range of 220 nm to 280 nm.

16. The AlN single crystal of claim 1 , wherein the AlN single crystal has an ultraviolet (UV) absorption coefficient of less than 30 cm −1 for an entire wavelength range of 210 nm to 220 nm.

17. The AlN single crystal of claim 16 , wherein the UV absorption coefficient is no less than approximately 5 cm −1 for the entire wavelength range of 210 nm to 220 nm.

18. The AlN single crystal of claim 1 , wherein the AlN single crystal has an ultraviolet (UV) absorption coefficient of less than 20 cm −1 for an entire wavelength range of 215 nm to 220 nm.

19. The AlN single crystal of claim 18 , wherein the UV absorption coefficient is no less than approximately 5 cm −1 for the entire wavelength range of 215 nm to 220 nm.

20. An AlN single crystal having a diameter that increases, along at least a portion of a length of the AlN single crystal, from a minimum diameter to a maximum diameter, the AlN single crystal having (i) a crystal augmentation parameter (CAP), in mm, greater than 20, and (ii) a ratio of an expansion length of the AlN single crystal, in mm, to the maximum diameter, in mm, ranging from approximately 0.002 to approximately 0.03, the CAP being defined by:

CAP

Assignees

• Bondokov Robert T
• Miebach Thomas
• Chen Jianfeng
• Suzuki Takashi
• Schowalter Leo J
• Crystal Is Inc

Inventors

• Bondokov Robert T
• Miebach Thomas
• Chen Jianfeng
• Suzuki Takashi
• Schowalter Leo J

Classifications

• Y02P70/50

  Manufacturing or production processes characterised by the final manufactured product · CPC title

• C30B23/06 Primary

  Heating of the deposition chamber, the substrate or the materials to be evaporated · CPC title

• C30B29/403

  AIII-nitrides · CPC title

• C30B25/20

  the substrate being of the same materials as the epitaxial layer · CPC title

• C30B23/025

  characterised by the substrate · CPC title