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Method for growing group III-nitride crystals in a mixture of supercritical ammonia and nitrogen, and group III-nitride crystals grown thereby achieved

Foreign code F110003791
File No. E06744US1
Posted date Jul 5, 2011
Country United States of America
Application number 97766107
Gazette No. 20080102016
Gazette No. 7803344
Date of filing Oct 25, 2007
Gazette Date May 1, 2008
Gazette Date Sep 28, 2010
Priority data
  • 2006US-60854567 (Oct 25, 2006) US
Title Method for growing group III-nitride crystals in a mixture of supercritical ammonia and nitrogen, and group III-nitride crystals grown thereby achieved
Abstract (US7803344)
A method of growing group III-nitride crystals in a mixture of supercritical ammonia and nitrogen, and the group-III crystals grown by this method.
The group III-nitride crystal is grown in a reaction vessel in supercritical ammonia using a source material or nutrient that is polycrystalline group III-nitride, amorphous group III-nitride, group-III metal or a mixture of the above, and a seed crystal that is a group-III nitride single crystal.
In order to grow high-quality group III-nitride crystals, the crystallization temperature is set at 550° C. or higher.
Theoretical calculations show that dissociation of NH3 at this temperature is significant.
However, the dissociation of NH3 is avoided by adding extra N2 pressure after filling the reaction vessel with NH3.
Scope of claims [claim1]
1. An ammonothermal method for growing group III-nitride crystals, comprising: (a) loading group III-containing source materials, group III-nitride seed crystals, and mineralizers into a reaction vessel;
(b) filling the reaction vessel with ammonia;
(c) adding extra nitrogen (N2) pressure in the reaction vessel to avoid disassociation of the ammonia into N2 and H2;
(d) raising the reaction vessel's temperature to attain a supercritical state for the ammonia; and
(e) ammonothermally growing the group III-nitride crystals, wherein convection of the supercritical ammonia transfers the source materials and deposits the transferred source materials onto the seed crystals.
[claim2]
2. The method of claim 1, wherein the extra nitrogen (N2) pressure in the adding step (c) is more than 100 atm.
[claim3]
3. The method of claim 2, wherein the group III-containing source materials are either metallic Ga, polycrystalline GaN, amorphous GaN or a mixture thereof, and the group III-nitride seed crystals are GaN.
[claim4]
4. The method of claim 3, wherein the reaction vessel is divided into a dissolution region and a crystallization region with a convection-restricting device, the group III-containing source materials are placed in a dissolution region, the group III-nitride seed crystals are placed in the crystallization region, and the crystallization region's temperature is maintained at 550 deg. C. or higher.
[claim5]
5. The method of claim 4, wherein the mineralizers contain at least one substance selected from LiNH2, NaNH2, and KNH2, and the dissolution region's temperature is maintained lower than the crystallization region's temperature.
[claim6]
6. The method of claim 5, wherein an inner surface of the reaction vessel is protected with a liner material containing vanadium.
[claim7]
7. The method of claim 4, wherein the mineralizers contain at least one substance selected from NH4F, NH4Cl, NH4Br, and NH4I, and the dissolution region's temperature is maintained higher than the crystallization region's temperature.
[claim8]
8. The method of claim 7, wherein an inner surface of the reaction vessel is protected with a liner material containing platinum or palladium.
[claim9]
9. The method of claim 4, wherein the group III-containing source materials contain metallic Ga and the method further comprises transforming the metallic Ga into a substance that contains Ga and N.
[claim10]
10. The method of claim 9, wherein the transforming step further comprises holding the reaction vessel's temperature lower than 300 deg. C. for more than 1 hour before raising the reaction vessel's temperature for crystal growth.
[claim11]
11. The method of claim 10, wherein the mineralizers contain at least one substance selected from LiNH2, NaNH2, and KNH2, and the dissolution region's temperature is maintained lower than the crystallization region's temperature.
[claim12]
12. The method of claim 11, wherein an inner surface of the reaction vessel is protected with a liner material containing vanadium.
[claim13]
13. The method of claim 10, wherein the mineralizers contain at least one substance selected from NH4F, NH4Cl, NH4Br, and NH4I, and the dissolution region's temperature is maintained higher than the crystallization region's temperature.
[claim14]
14. The method of claim 13, wherein an inner surface of the reaction vessel is protected with a liner material containing platinum or palladium.
[claim15]
15. A group III-nitride crystal grown by the method of claim 1.
[claim16]
16. The group III-nitride crystal of claim 15, further comprising a single crystalline group III-nitride crystal.
[claim17]
17. The group III-nitride crystal of claim 16, further comprising a single crystalline group III-nitride wafer sliced from the single crystalline group III-nitride crystal.
[claim18]
18. The group III-nitride crystal of claim 15, wherein the group III-nitride crystal is a gallium nitride crystal.
  • Inventor, and Inventor/Applicant
  • HASHIMOTO TADAO
  • JAPAN SCIENCE AND TECHNOLOGY AGENCY
IPC(International Patent Classification)
Reference ( R and D project ) ERATO NAKAMURA Inhomogeneous Crystal AREA
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