Process for large-scale ammonothermal manufacturing of semipolar gallium nitride boules
View Patent ↗Methods for large-scale manufacturing of semipolar gallium nitride boules are disclosed. The disclosed methods comprise suspending large-area single crystal seed plates in a rack, placing the rack in a large diameter autoclave or internally-heated high pressure apparatus along with ammonia and a mineralizer, and growing crystals ammonothermally. A bi-faceted growth morphology may be maintained to facilitate fabrication of large area semipolar wafers without growing thick boules.
1. A crystalline substrate comprising:
at least one planar surface angled by at least about 5 degrees from an m-plane and a c-plane of said crystalline substrate; and
alternating first and second bands laterally disposed on said planar surface, said first band comprising a first impurity concentration, said second band comprising a second impurity concentration, wherein said first impurity concentration is higher than said second concentration.
2. The substrate of claim 1 , wherein said planar surface has a semipolar orientation within about 3 degrees of one of {6 0 −6 −1}, {5 0 −5 −1}, {4 0 −4 −1}, {3 0 −3 −1}, {5 0 −5 −2}, {2 0 −2 −1}, {3 0 −3 −2}, {4 0 −4 −3}, and {5 0 −5 −4}.
3. The substrate of claim 1 , wherein the length of said planar surface is greater than about 25 millimeters.
4. The substrate of claim 1 , wherein said planar surface has a dislocation density below about 10 7 cm −2 .
5. The substrate of claim 4 , wherein said dislocation density is below about 10 6 cm −2 .
6. The substrate of claim 5 , wherein said dislocation density is below about 10 5 cm −2 .
7. The substrate of claim 6 , wherein said dislocation density is below about 10 4 cm −2 .
8. The substrate of claim 1 , wherein the crystallographic orientation of said planar surface has a full width at half maximum of a symmetric x-ray rocking curve less than about 150 arc seconds.
9. The substrate of claim 8 , wherein said full width at half maximum of a symmetric x-ray rocking curve is less than about 100 arc seconds.
10. The substrate of claim 1 , wherein the crystalline substrate has a substantially wurtzite structure, and is substantially free of other crystal structures, wherein the other structures are less than about 1% in volume with respect to a volume of the substantially wurtzite structure.
11. The substrate of claim 1 , wherein the crystallographic orientation of said planar surface has a full width at half maximum of a lowest-order asymmetric x-ray rocking curve less than about 150 arc seconds.
12. The substrate of claim 11 , wherein said full width at half maximum of a lowest-order asymmetric x-ray rocking curve is less than about 100 arc seconds.
13. The substrate of claim 1 , wherein said first and second bands have a period between about 0.01 mm and about 100 mm.
14. The substrate of claim 13 , wherein said period is between about 1 mm and about 10 mm.
15. The substrate of claim 1 , wherein the ratio of said first and second concentrations is less than 40.
16. The substrate off claim 15 , wherein said ratio of said first and second impurity concentrations is less than 10.
17. The substrate of claim 1 , wherein said alternating first and second bands comprise at least 4 of each of said first and second bands.
18. The substrate of claim 1 , wherein said crystalline substrate comprises a gallium-containing nitride.
19. The substrate of claim 1 , wherein said first and second impurity concentrations are greater than about 10 16 cm −3 of at least one impurity selected from O, H, Li, Na, K, F, Cl, Br, I, Si, Ge, Cu, Mn, and Fe.
20. The substrate of claim 19 , wherein the at least one impurity is selected from O and H, and the distribution comprises at least 8 of each of said first and second bands, wherein said ratio of said first and second impurity concentrations is less than about 2.
21. The substrate of claim 1 , wherein each of said first and second bands comprise a plurality of impurities constituting said first and second impurity concentrations.