High resistivity silicon carbide single crystal
The purpose of the invention is to provide a high resistivity silicon carbide substrate with electrical properties and structural quality suitable for subsequent device manufacturing, such as for example high frequency devices, so that the devices can exhibit stable and linear characteristics and to provide a high resistivity silicon carbide substrate having a low density of structural defects and a substantially controlled uniform radial distribution of its resistivity.
1. A semi-insulating silicon carbide single crystal having a resistivity of at least 10 5 Ω·cm at 25° C., comprising:
at least one deep impurity; and
at least one deep intrinsic defect,
wherein a concentration of the at least one deep impurity is sufficient to affect the resistivity of the crystal by compensating either shallow donors or shallow acceptors, but said concentration being lower than the concentration of deep intrinsic defects.
2. The silicon carbide crystal according to claim 1 , wherein said at least one deep intrinsic defect has deep donor levels, and said at least one deep impurity has deep acceptor levels.
3. The silicon carbide crystal according to claim 2 , wherein said at least one deep impurity has at least one level located in the upper half of the band gap.
4. The silicon carbide crystal according to claim 1 , comprising at least two deep impurities, wherein two deep impurities are Titanium and Boron.
5. The silicon carbide crystal according to claim 1 , wherein said at least one deep impurity is Titanium.
6. The silicon carbide crystal according to claim 1 , wherein said at least one deep impurity is Boron.
7. The silicon carbide crystal according to claim 1 , wherein said at least one deep intrinsic defect is a carbon vacancy or a single or a complex intrinsic defect related to the carbon site.
8. The silicon carbide crystal according to claim 1 , wherein said at least one deep impurity is chosen from the IIIB, IVB, VB, VIB, VIIB or IIIA periodic columns.
9. The silicon carbide crystal according to claim 8 , wherein said at least one deep impurity is either Sc, Ti, Nb, Cr, Mo, W, Mn, Fe, Co, Ni, B, or Ga.
10. The silicon carbide crystal according to claim 1 , wherein said at least one deep intrinsic defect has a deep acceptor level, and said at least one deep impurity has a deep donor level.
11. The silicon carbide crystal according to claim 10 , wherein said at least one deep intrinsic defect is a silicon vacancy.
12. The silicon carbide crystal according to claim 10 , wherein said at least one deep impurity has at least one level located in the lower half of the band gap of the semiconductor.
13. The silicon carbide crystal according to claim 1 , wherein said at least one deep impurity is chosen from the transition metals from the IIB, IVB, VB, VIB, VIIB or from the VA periodic columns.
14. The silicon carbide crystal according to claim 13 , wherein said at least one deep impurity is either Ta, Zn or Mo.
15. The silicon carbide crystal according to claim 1 , wherein the concentration of said at least one deep impurity is less than 10 16 cm −3 .
16. The silicon carbide crystal according to claim 1 , wherein the concentration of said at least one deep impurity is less than 5×10 15 cm −3 .
17. The silicon carbide crystal according to claim 1 , wherein the concentration of said at least one deep impurity is sufficient to provide a uniform distribution of said resistivity in the crystal.
18. The silicon carbide crystal according to claim 1 , wherein the polytype of the crystal is selected from the group consisting of: 4H, 6H, 15R and 3C.
19. The silicon carbide crystal according to claim 1 , wherein said at least one deep impurity is introduced into the crystal during a crystal growth process.
20. The silicon carbide crystal according to claim 1 , wherein said resistivity of the crystal measured at 25° C. does not substantially decrease after annealing the crystal at temperatures up to 1700° C.
21. The silicon carbide crystal according to claim 1 , wherein an activation energy of said resistivity of the crystal remains substantially unchanged after annealing the crystal at temperatures up to 1700° C.