Group III nitride semiconductor multilayer structure and production method thereof

1. A Group III nitride semiconductor multilayer structure which is a Group III nitride semiconductor multilayer structure where an AlN crystal film having a crystal grain boundary interval of 200 nm or more is formed as a seed layer on a C-plane sapphire substrate surface by a sputtering method and an underlying layer, an n-type semiconductor layer, a light-emitting layer and a p-type semiconductor layer, each composed of a Group III nitride semiconductor, are further stacked, wherein regions in which said seed layer is present and is absent are formed on said C-plane sapphire substrate surface and/or regions capable of epitaxial growth and incapable of epitaxial growth are formed in said underlying layer.

2. The Group III nitride semiconductor multilayer structure as claimed in claim 1 , wherein the full width at half maximum of the X-ray diffraction rocking curve of (0002) plane and (10-10) of the AlN crystal film are 100 arcsec or less and 1.7° or less, respectively.

3. The Group III nitride semiconductor multilayer structure as claimed in claim 1 , wherein the oxygen content in the AlN crystal film is 5 atm % or less.

4. The Group III nitride semiconductor multilayer structure as claimed in claim 1 , wherein the sapphire substrate has an off-angle of 0.1 to 0.7°.

5. The Group III nitride semiconductor multilayer structure as claimed in claim 1 , wherein the sputtering method is an RF sputtering method.

6. The Group III nitride semiconductor multilayer structure as claimed in claim 1 , wherein the AlN crystal film is deposited by a sputtering method by placing the sapphire substrate in plasma.

7. The Group III nitride semiconductor multilayer structure as claimed in claim 1 , wherein the sapphire substrate surface is subjected to an N 2 plasma or O 2 plasma treatment and then the AlN crystal film is deposited on said sapphire substrate surface.

8. The Group III nitride semiconductor multilayer structure as claimed in claim 1 , wherein the substrate temperature during deposition of the AlN crystal film on the sapphire substrate surface is from 300 to 800° C.

9. The Group III nitride semiconductor multilayer structure as claimed in claim 1 , wherein the thickness of the AlN crystal film is from 10 to 50 nm.

10. The Group III nitride semiconductor multilayer structure as claimed in claim 9 , wherein the thickness of the AlN crystal film is from 25 to 35 nm.

11. The Group III nitride semiconductor multilayer structure as claimed in claim 1 , wherein the diameter of the sapphire substrate is 100 mm or more.

12. The Group III nitride semiconductor multilayer structure as claimed in claim 1 , wherein the full width at half maximum of the X-ray diffraction rocking curve of the p-contact layer as the final p-type semiconductor layer is 60 arcsec or less and 250 arcsec or less on the (0002) plane and the (10-10) plane, respectively.

13. The Group III nitride semiconductor multilayer structure as claimed in claim 1 , wherein the underlying layer is a GaN or AlGaN crystal.

14. A light-emitting device comprising the Group III nitride semiconductor multilayer structure claimed in claim 1 .

15. The light-emitting device as claimed in claim 14 , wherein a negative electrode and a positive electrode are provided on the n-type semiconductor layer and the p-type semiconductor layer, respectively.

16. A lamp comprising the light-emitting device claimed in claim 14 .

17. An electronic device having incorporated therein the lamp claimed in claim 16 .

18. A mechanical device having incorporated therein the electronic device claimed in claim 17 .