Large, UV-transparent aluminum nitride single crystals

Patent metadata

Field	Value
Publication number	US-11828002-B2
Application number	US-202117181138-A
Country	US
Kind code	B2
Filing date	Feb 22, 2021
Priority date	Nov 10, 2017
Publication date	Nov 28, 2023
Grant date	Nov 28, 2023

Abstract

In various embodiments, single-crystal aluminum nitride boules and substrates having high transparency to ultraviolet light and low defect density are formed. The single-crystal aluminum nitride may function as a platform for the fabrication of light-emitting devices such as light-emitting diodes and lasers.

First claim

What is claimed is:

1. A method of forming single-crystal aluminum nitride (AlN), the method comprising:
providing a bulk polycrystalline AlN ceramic;
disposing at least a portion of the AlN ceramic into a first crucible;
annealing and densifying the at least a portion of the AlN ceramic in the first crucible, thereby forming a polycrystalline AlN source, the annealing and densifying comprising:
(i) heating the at least a portion of the AlN ceramic at a first temperature ranging from 1100° C. to 1900° C. for a first time ranging from 2 hours to 25 hours, and (ii) thereafter, heating the at least a portion of the AlN ceramic at a second temperature ranging from 1900° C. to 2250° C. for a second time ranging from 3 hours to 15 hours, or
(i) heating the at least a portion of the AlN ceramic during a temperature ramp to a third temperature ranging from 1900° C. to 2250° C. over a third time ranging from 5 hours to 25 hours, and (ii) thereafter, heating the at least a portion of the AlN ceramic at a fourth temperature ranging from 1900° C. to 2250° C. for a fourth time ranging from 3 hours to 25 hours;

cooling the AlN source to approximately room temperature;
disposing within a furnace a second crucible containing the AlN source and a seed crystal comprising single-crystal AlN;
heating the second crucible with the furnace to a growth temperature of at least 2000° C.;
maintaining the second crucible at the growth temperature for a soak time ranging from 1 hour to 10 hours;
after the soak time, while the second crucible is at the growth temperature, (i) condensing vapor comprising aluminum and nitrogen on the seed crystal, thereby forming a single-crystalline AlN boule extending from the seed crystal, and (ii) moving the second crucible relative to the furnace, a growth rate of the AlN boule being approximately equal to a rate of relative motion between the second crucible and the furnace;
thereafter, cooling the AlN boule via a cooling cycle comprising:
cooling the AlN boule from the growth temperature to a fifth temperature ranging from 1000° C. to 1650° C. over a fifth time ranging from 1 hour to 10 hours; and
thereafter, cooling the AlN boule to approximately room temperature.

2. The method of claim 1 , wherein the growth temperature is approximately 2300° C. or less.

3. The method of claim 1 , wherein a diameter of at least a portion of the AlN boule is at least approximately 50 mm.

4. The method of claim 1 , wherein a diameter of at least a portion of the AlN boule is approximately 50 mm.

5. The method of claim 1 , further comprising introducing oxygen into the second crucible during formation of the single-crystalline AlN boule extending from the seed crystal.

6. The method of claim 1 , further comprising, prior to disposing the at least a portion of the AlN ceramic into the first crucible, fragmenting the AlN ceramic into fragments each having a width greater than approximately 0.5 cm and less than approximately 2 cm, whereby the at least a portion of the AlN ceramic comprises at least some of the fragments.

7. The method of claim 1 , wherein a crystalline orientation of the seed crystal is substantially parallel to a c-axis.

8. The method of claim 1 , wherein the first crucible and the second crucible are the same crucible.

9. The method of claim 1 , wherein the first crucible and the second crucible are different crucibles.

10. The method of claim 1 , wherein the growth rate is at least 0.5 mm/hour.

11. The method of claim 1 , wherein the soak time is approximately 5 hours.

12. The method of claim 1 , wherein a diameter of the seed crystal is approximately 35 mm or larger.

13. The method of claim 1 , further comprising slicing the AlN boule to form a single-crystalline AlN substrate having a diameter of at least 50 mm.

14. The method of claim 13 , further comprising fabricating a light-emitting device over at least a portion of the AlN substrate.

15. The method of claim 14 , wherein the light-emitting device is configured to emit ultraviolet light.

16. The method of claim 14 , further comprising, after forming at least a portion of the light-emitting device, removing at least a portion of the AlN substrate from the light-emitting device.

17. The method of claim 14 , wherein the light-emitting device comprises a light-emitting diode or a laser.

18. The method of claim 1 , further comprising gettering oxygen and/or carbon during formation of the single-crystalline AlN boule.

19. The method of claim 18 , wherein the oxygen and/or carbon are gettered with a gettering material introduced into the second crucible and/or the furnace prior to and/or during formation of the single-crystalline AlN boule.

Assignees

• Bondokov Robert T
• Chen Jianfeng
• Yamaoka Keisuke
• Wang Shichao
• Rao Shailaja P
• Suzuki Takashi
• Schowalter Leo J
• Crystal Is Inc

Inventors

• Bondokov Robert T
• Chen Jianfeng
• Yamaoka Keisuke
• Wang Shichao
• Rao Shailaja P
• Suzuki Takashi
• Schowalter Leo J

Classifications

• H10P14/2908

  Nitrides · CPC title

• H10H20/0137 Primary

  the light-emitting regions comprising nitride materials · CPC title

• C30B29/403 Primary

  AIII-nitrides · CPC title

• C01B21/072

  with aluminium · CPC title

• C30B23/002

  Controlling or regulating · CPC title