Method and apparatus for producing large, single-crystals of aluminum nitride
Bulk single crystals of AlN having a diameter greater than about 25 mm and dislocation densities of about 10,000 cm −2 or less and high-quality AlN substrates having surfaces of any desired crystallographic orientation fabricated from these bulk crystals.
1. An aluminum nitride single-crystal substrate having a diameter greater than about 25 mm, a thickness of less than about 1 mm, a dislocation density less than about 10,000 cm −2 , and a surface substantially all of which has a single crystalline orientation.
2. The single-crystal substrate of claim 1 wherein the average dislocation density is less than about 5,000 cm −2 .
3. The single-crystal substrate of claim 2 wherein the average dislocation density is less than about 1,000 cm −2 .
4. The single-crystal substrate of claim 3 wherein the average dislocation density is less than about 500 cm −2 .
5. The single-crystal substrate of claim 4 wherein the average dislocation density is less than about 100 cm −2 .
6. The single-crystal substrate of claim 5 having at least one region substantially devoid of dislocation defects, the at least one region having an area exceeding 25 mm 2 .
7. The single-crystal substrate of claim 1 wherein the crystallographic orientation is selected from the group consisting of: {0001}, {10 1 0} and {11 2 0}.
8. The single-crystal substrate of claim 1 , further comprising at least one strained layer epitaxially grown thereover, the at least one strained layer comprising a material selected from the group consisting of AlN, GaN, InN, and any binary or tertiary alloy combination thereof, wherein an average dislocation density within the at least one strained layer is less than about 10,000 cm −2 .
9. The single-crystal substrate of claim 1 wherein the thickness is about 350 μm.
10. The single-crystal substrate of claim 8 , further comprising at least one buffer layer disposed below the strained layer.
11. The single-crystal substrate of claim 10 wherein the at least one buffer layer comprises AlN.
12. The single-crystal substrate of claim 1 having a diameter greater than about 30 mm.
13. The single-crystal substrate of claim 1 having a diameter greater than about 50 mm.