Self-standing GaN substrate, GaN crystal, method for producing GaN single crystal, and method for producing semiconductor device
View Patent ↗An object is to provide a nonpolar or semipolar GaN substrate having improved size and crystal quality. A self-standing GaN substrate has an angle between the normal of the principal surface and an m-axis of 0 degrees or more and 20 degrees or less, wherein: the size of the projected image in a c-axis direction when the principal surface is vertically projected on an M-plane is 10 mm or more; and when an a-axis length is measured on an intersection line between the principal surface and an A-plane, a low distortion section with a section length of 6 mm or more and with an a-axis length variation within the section of 10.0×10 −5 Å or less is observed.
1. A self-standing GaN substrate having a first principal surface and a second principal surface, the first principal surface and the second principal surface facing away from each other, and having an angle between a normal of the first principal surface and an m-axis of 0 degrees or more and 20 degrees or less, wherein:
a first projected image obtained by vertically projecting the first principal surface on an M-plane has a size of 10 mm or more in a c-axis direction; and
when an a-axis length is measured on an intersection line between the first principal surface and an A-plane, a first section having a section length of 6 mm or more and an a-axis length variation within the first section of 10.0×10 −5 Å or less is observed.
2. The self-standing GaN substrate according to claim 1 , wherein the size of the first projected image in a c-axis direction is 15 mm or more, and the first section has a section length of 8 mm or more and an a-axis length variation within the section of 10.0×10 −5 Å or less.
3. The self-standing GaN substrate according to claim 2 , wherein the first section has a section length of 10 mm or more and an a-axis length variation within the section of 10.0×10 −5 Å or less.
4. The self-standing GaN substrate according to claim 3 , wherein the first section has a section length of 10 mm or more and an a-axis length variation within the section of 8.0×10 −5 Å or less.
5. The self-standing GaN substrate according to claim 1 , wherein a c-axis length variation in the first section is 3.0×10 −4 Å or less.
6. The self-standing GaN substrate according to claim 1 , wherein an X-ray rocking curve full-width at half-maximum of a (300) plane in the first section is less than 100 arcsec.
7. The self-standing GaN substrate according to claim 1 , wherein a variation width of an X-ray rocking curve full-width at half-maximum of a (300) plane in the first section is less than 20 arcsec.
8. The self-standing GaN substrate according to claim 1 , having a defect increasing zone extending in a direction intersecting an A-plane on the first principal surface.
9. The self-standing GaN substrate according to claim 1 , wherein a size of the first projected image in an a-axis direction is 30 mm or more.
10. The self-standing GaN substrate according to claim 1 , wherein a size of the first projected image in an a-axis direction is 40 mm or more.
11. The self-standing GaN substrate according to claim 1 , wherein the self-standing GaN substrate comprises a GaN crystal grown by an HVPE method.
12. The self-standing GaN substrate according to claim 1 , having an absorption coefficient at a wavelength of 450 nm is 2 cm −1 or less.
13. The self-standing GaN substrate according to claim 1 wherein the self-standing GaN substrate comprises fluorine.
14. The self-standing GaN substrate according to claim 1 , having an alkali metal concentration of lower than 1×10 15 cm −3 .
15. The self-standing GaN substrate according to claim 1 , wherein the self-standing GaN substrate comprises a stacking fault.