Aluminum nitride bulk crystals having high transparency to ultraviolet light and methods of forming them
First Claim
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1. A method of forming single-crystal AlN, the method comprising:
- providing a substantially undoped polycrystalline AlN ceramic having an oxygen concentration less than approximately 100 ppm within a crystal growth enclosure, the crystal growth enclosure being disposed within a furnace;
utilizing the polycrystalline AlN ceramic, forming a single-crystal bulk AlN crystal by a sublimation-recondensation process at a growth temperature greater than approximately 2000°
C.; and
after the sublimation-recondensation process, (i) cooling the bulk AlN crystal from the growth temperature to a first temperature between approximately 1500°
C. and approximately 1800°
C. at a first rate ranging from 70°
C./hour to 150°
C./hour, the first rate being slowed via controlled application of heat from the furnace, and (ii) thereafter, cooling the bulk AlN crystal from the first temperature to a second temperature lower than the first temperature at a second rate greater than approximately 250°
C./hour.
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Abstract
In various embodiments, methods of forming single-crystal AlN include providing a substantially undoped polycrystalline AlN ceramic having an oxygen concentration less than approximately 100 ppm, forming a single-crystal bulk AlN crystal by a sublimation-recondensation process at a temperature greater than approximately 2000° C., and cooling the bulk AlN crystal to a first temperature between approximately 1500° C. and approximately 1800° C. at a first rate less than approximately 250° C./hour.
203 Citations
35 Claims
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1. A method of forming single-crystal AlN, the method comprising:
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providing a substantially undoped polycrystalline AlN ceramic having an oxygen concentration less than approximately 100 ppm within a crystal growth enclosure, the crystal growth enclosure being disposed within a furnace; utilizing the polycrystalline AlN ceramic, forming a single-crystal bulk AlN crystal by a sublimation-recondensation process at a growth temperature greater than approximately 2000°
C.; andafter the sublimation-recondensation process, (i) cooling the bulk AlN crystal from the growth temperature to a first temperature between approximately 1500°
C. and approximately 1800°
C. at a first rate ranging from 70°
C./hour to 150°
C./hour, the first rate being slowed via controlled application of heat from the furnace, and (ii) thereafter, cooling the bulk AlN crystal from the first temperature to a second temperature lower than the first temperature at a second rate greater than approximately 250°
C./hour. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method of forming single-crystal AlN, the method comprising:
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providing a polycrystalline AlN ceramic within a crystal growth enclosure, the crystal growth enclosure being disposed within a furnace; utilizing the polycrystalline AlN ceramic, forming a single-crystal bulk AlN crystal by a sublimation-recondensation process at a growth temperature greater than approximately 2000°
C.; andafter the sublimation-recondensation process, (i) cooling the bulk AlN crystal from the growth temperature to a first temperature between approximately 1500°
C. and approximately 1800°
C. at a first rate ranging from 70°
C./hour to 150°
C./hour, the first rate being slowed via controlled application of heat from the furnace, and (ii) thereafter, cooling the bulk AlN crystal from the first temperature to a second temperature lower than the first temperature at a second rate greater than approximately 250°
C./hour. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
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Specification