High-pressure vessel for growing group III nitride crystals and method of growing group III nitride crystals using high-pressure vessel and group III nitride crystal
원문보기
IPC분류정보
국가/구분
United States(US) Patent
등록
국제특허분류(IPC7판)
C01B-021/06
C30B-023/00
C23C-016/00
출원번호
US-0455683
(2009-06-04)
등록번호
US-8236267
(2012-08-07)
발명자
/ 주소
Hashimoto, Tadao
Letts, Edward
Ikari, Masanori
출원인 / 주소
Sixpoint Materials, Inc.
대리인 / 주소
K&L Gates, LLP
인용정보
피인용 횟수 :
10인용 특허 :
17
초록▼
The present invention discloses a high-pressure vessel of large size formed with a limited size of e.g. Ni—Cr based precipitation hardenable superalloy. The vessel may have multiple zones. For instance, the high-pressure vessel may be divided into at least three regions with flow-restricting devices
The present invention discloses a high-pressure vessel of large size formed with a limited size of e.g. Ni—Cr based precipitation hardenable superalloy. The vessel may have multiple zones. For instance, the high-pressure vessel may be divided into at least three regions with flow-restricting devices and the crystallization region is set higher temperature than other regions. This structure helps to reliably seal both ends of the high-pressure vessel, and at the same time, may help to greatly reduce unfavorable precipitation of group III nitride at the bottom of the vessel. This invention also discloses novel procedures to grow crystals with improved purity, transparency and structural quality. Alkali metal-containing mineralizers are charged with minimum exposure to oxygen and moisture until the high-pressure vessel is filled with ammonia. Several methods to reduce oxygen contamination during the process steps are presented. Also, back etching of seed crystals and a new temperature ramping scheme to improve structural quality are disclosed.
대표청구항▼
1. A cylindrical high-pressure vessel having a chamber and suitable to grow group III nitride crystals comprising a main body and two lids, one on each end of the main body, the main body being made of precipitation hardenable Ni—Cr based superalloy, having its longest dimension along the vertical d
1. A cylindrical high-pressure vessel having a chamber and suitable to grow group III nitride crystals comprising a main body and two lids, one on each end of the main body, the main body being made of precipitation hardenable Ni—Cr based superalloy, having its longest dimension along the vertical direction, its inner diameter larger than 2 inches, its minimum outer diameter larger than 4 inches, its vertical length of the main body more than 5 times the inner diameter, and further comprising the following features: (a) the chamber of the high-pressure vessel is divided into at least three regions along the vertical direction with flow-restricting baffles comprising regions closest to the both lids and a crystallization region;(b) the crystallization region is located between the regions closest to the both lids and is configured to be maintained at a temperature greater than said regions closest to the both lids during crystal growth;(c) the regions closest to the both lids are configured to be maintained at a lower temperature than other regions during crystal growth;(d) and a nutrient region is located above the crystallization region, wherein(e) the main body is made of forged round rod or forged hollow rod of which a primary forging pressure is applied along the radial direction of an original billet;(f) the two lids on the both ends are closed with clamps; and(g) the clamps are made of forged disks of precipitation hardenable Ni—Cr based superalloy of which the primary forging pressure is applied along the longitudinal direction of an original billet from which the disk are formed. 2. A cylindrical high-pressure vessel having a chamber and suitable to grow group III nitride crystals comprising a main body and two lids, one on each end of the main body, the main body being made of precipitation hardenable Ni—Cr based superalloy, having its longest dimension along the vertical direction, its inner diameter larger than 2 inches, its minimum outer diameter larger than 4 inches, its vertical length of the main body more than 5 times the inner diameter, and further comprising the following features: (a) the chamber of the high-pressure vessel is divided into at least three regions along the vertical direction with flow-restricting baffles comprising regions closest to the both lids and a crystallization region;(b) the crystallization region is located between the regions closest to the both lids and is configured to be maintained at a temperature greater than said regions closest to the both lids during crystal growth;(c) the regions closest to the both lids are configured to be maintained at a lower temperature than other regions during crystal growth;(d) and a nutrient region is located above the crystallization region, wherein at least the high-pressure vessel and heaters for the vessel are housed in a blast containment enclosure of which the wall thickness is more than ½ inch, and wherein an ammonia release valve within the blast containment enclosure is operable remotely from outside of the blast containment enclosure. 3. A cylindrical high-pressure vessel having a chamber and suitable to grow group III nitride crystals comprising a main body and two lids, one on each end of the main body, the main body being made of precipitation hardenable Ni—Cr based superalloy, having its longest dimension along the vertical direction, its inner diameter larger than 2 inches, its minimum outer diameter larger than 4 inches, its vertical length of the main body more than 5 times the inner diameter, and further comprising the following features: (a) the chamber of the high-pressure vessel is divided into at least three regions along the vertical direction with flow-restricting baffles comprising regions closest to the both lids and a crystallization region;(b) the crystallization region is located between the regions closest to the both lids and is configured to be maintained at a temperature greater than said regions closest to the both lids during crystal growth;(c) the regions closest to the both lids are configured to be maintained at a lower temperature than other regions during crystal growth;(d) and a nutrient region is located above the crystallization region, wherein(e) the main body is made of forged round rod or forged hollow rod of which the grain flow is along the longitudinal direction of the original billet;(f) the two lids on the both ends are closed with clamps; and(g) the clamps are made of forged disks of precipitation hardenable Ni—Cr based superalloy of which the grain flow is along the radial direction of an original billet from which the disks are formed. 4. A cylindrical high-pressure vessel for growing group III nitride crystals of any of claims 1,2, or 3 wherein one or more buffer spaces are created with flow restricting baffles between the crystallization region and the nutrient region. 5. A cylindrical high-pressure vessel for growing group III nitride crystals of claim 4 wherein the height of the buffer spaces are at least ⅕ of the inner diameter of the high-pressure vessel. 6. A cylindrical high-pressure vessel for growing group III nitride crystals of any of claims 1,2, or 3 wherein a heater for the crystallization region is configured to provide a temperature greater than 550° C. 7. A reactor for ammonothermal growth of a group III-nitride crystalline ingot comprising (a) a body defining a chamber(b) a first clamp for sealing an end of the reactor, wherein the first clamp is formed of a metal or alloy having a grain flow in a radial direction in the clamp, and wherein the clamp is formed of precipitation hardenable Ni—Cr based superalloy. 8. A reactor according to claim 7 and further comprising a blast containment enclosure of which the wall thickness is more than ½ inch, and wherein an ammonia release valve within the blast containment enclosure is operable remotely from outside of the blast containment enclosure. 9. A reactor according to claim 7 wherein the first heater is configured to maintain the nutrient region of the reactor at a temperature near but greater than a temperature of the reactor in a crystallization region of the reactor when said reactor is configured to grow a gallium nitride crystal having retrograde solubility in supercritical ammonia. 10. A reactor according to claim 9 wherein the first heater is configured to maintain the nutrient region no more than about 30° C. greater than the temperature of the crystallization region. 11. A reactor according to claim 7 and further comprising a second clamp for sealing a second end of the reactor. 12. A reactor for ammonothermal growth of a group III-nitride crystalline ingot comprising (a) a body defining a chamber(b) a first heater for heating a nutrient region of the reactor(c) a second heater for heating a crystallization region of the reactor(d) a third region selected from a buffer region, said buffer region being defined by a plurality of baffles comprising a first end baffle and an opposite end baffle with one or more optional baffles therebetween, and a distance from the first end baffle to the opposite end baffle of the plurality is at least ⅕ of an inner diameter of the reactor; and an end region(e) at least one baffle separating the crystallization region from the nutrient region or the crystallization region from an end region of the reactor(f) and a clamp made from a forged disk of precipitation hardenable Ni—Cr based superalloy of which the primary forging pressure is applied along the longitudinal direction of an original billet from which the forged disk was formed. 13. A reactor according to claim 12 or claim 8 wherein the third region is a buffer region. 14. A reactor according to claim 13 wherein the reactor further comprises the end region. 15. A reactor according to claim 12 or claim 8 wherein the third region is an end region. 16. A reactor according to claim 15 wherein the clamp of said end region is formed of a metal or alloy having a grain flow in a radial direction in the clamp. 17. A kit for ammonothermal growth of a group III-nitride crystalline ingot comprising (a) a reactor of claim 12 or claim 8 and(b) a mineralizer in an encapsulant, wherein the encapsulant is an oxygen-and water-impermeable material capable of rupturing to release the mineralizer under growth conditions in the reactor. 18. A kit according to claim 17 wherein the encapsulant is a metal or alloy coating on the mineralizer that softens or melts at crystal growth conditions in the reactor. 19. A kit according to claim 17 wherein the encapsulant comprises a water- and oxygen-impermeable container that ruptures under crystal growth conditions in the reactor. 20. A kit according to claim 19 wherein a chamber defined by the container and containing the encapsulant has a pressure much less than a pressure within the reactor under crystal growth conditions so that the encapsulant ruptures as pressure exceeds a cracking pressure of the encapsulant as pressure increases to crystal growth conditions within the reactor.
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