Method for growing nitride semiconductor

1. A method for growing a nitride semiconductor, said method comprising:

forming a surface reformation layer directly on a sapphire substrate in a lower temperature than a growth temperature of the nitride semiconductor;

after the forming of the surface reformation layer, raising a temperature of the sapphire substrate with the surface reformation layer formed thereon from the lower temperature than the growth temperature of the nitride semiconductor up to the growth temperature of the nitride semiconductor in an atmosphere including ammonia; and

growing a nitride semiconductor layer on a surface of the surface reformation layer by using a metal-organic vapor phase epitaxy (MOVPE) method or a halide vapor phase epitaxy (HVPE) method, and

wherein the surface reformation layer has a thickness in a range of 1 to 10 nm.

2. The method according to claim 1 , wherein:

the surface reformation layer comprises a nitrided layer.

3. The method according to claim 1 , wherein forming the surface reformation layer comprises forming the surface reformation layer by plasma irradiation.

4. The method according to claim 3 , wherein the surface reformation layer comprises at least Al, N, Si, and O atoms, and

wherein the plasma comprises a gas plasma including a gas containing nitrogen atom and a gas containing silicon atom.

5. The method according to claim 1 , wherein growing the nitride semiconductor layer comprises adjusting a growth temperature of a region of the nitride semiconductor layer grown in contact with the surface reformation layer to be not less than 900° C.

6. The method according to claim 1 , wherein raising the temperature of the sapphire substrate comprises introducing ammonia when the temperature of the sapphire substrate is not more than 800° C.

7. The method according to claim 1 , wherein raising the temperature of the sapphire substrate comprises starting to introduce the ammonia when a temperature of the sapphire substrate is not more than 300° C.

8. The method according to claim 1 , wherein growing the nitride semiconductor layer comprises controlling a mean value of an X-ray diffraction half width of the nitride semiconductor layer to be not more than 290 seconds when the nitride semiconductor layer is grown repeatedly 100 times under a same condition.

9. The method according to claim 1 , wherein the temperature of the sapphire substrate with the surface reformation layer formed thereon is raised from a room temperature up to the growth temperature of the nitride semiconductor in the atmosphere including ammonia.

10. The method according to claim 1 , wherein said growing the nitride semiconductor layer on the surface of the surface reformation layer is performed by the HVPE method.

11. A method for producing a nitride semiconductor, said method comprising:

forming a surface reformation layer directly on a sapphire substrate in a lower temperature than a growth temperature of the nitride semiconductor;

after the forming of the surface reformation layer, raising a temperature of the sapphire substrate with the surface reformation layer formed thereon from the lower temperature than the growth temperature of the nitride semiconductor up to the growth temperature of the nitride semiconductor in an atmosphere including an inert gas, or an atmosphere including the inert gas and hydrogen at a concentration of 10% or less relative to the inert gas; and

growing a nitride semiconductor layer on a surface of the surface reformation layer by using a metal-organic vapor phase epitaxy (MOVPE) method or a halide vapor phase epitaxy (HVPE) method, and

wherein the surface reformation layer has a thickness in a range of 1 to 10 nm.

12. The method according to claim 11 , wherein:

the surface reformation layer comprises a nitrided layer.

13. The method according to claim 11 , wherein forming the surface reformation layer comprises forming the surface reformation layer by plasma irradiation.

14. The method according to claim 13 , wherein the surface reformation layer comprises at least Al, N, Si, and O atoms, and

wherein the plasma comprises a gas plasma including a gas containing nitrogen atom and a gas containing silicon atom.

15. The method according to claim 11 , wherein growing the nitride semiconductor layer comprises adjusting a growth temperature of a region of the nitride semiconductor layer grown in contact with the surface reformation layer to be not less than 900° C.

16. The method according to claim 11 , wherein raising the temperature of the sapphire substrate comprises introducing the inert gas, or the inert gas and hydrogen at a concentration of 10% or less relative to the inert gas when the temperature of the sapphire substrate is not more than 800° C.

17. The method according to claim 11 , wherein raising the temperature of the sapphire substrate comprises starting to introduce the inert gas, or the inert gas and hydrogen at a concentration of 10% or less relative to the inert gas when a temperature of the sapphire substrate is not more than 300° C.

18. The method according to claim 11 , wherein growing the nitride semiconductor layer comprises controlling a mean value of an X-ray diffraction half width of the nitride semiconductor layer to be not more than 290 seconds when the nitride semiconductor layer is grown repeatedly 100 times under a same condition.

19. The method according to claim 11 , wherein the temperature of the sapphire substrate with the surface reformation layer formed thereon is raised from a room temperature up to the growth temperature of the nitride semiconductor in the atmosphere including the inert gas, or the atmosphere including the inert gas and hydrogen at said concentration of 10% or less relative to the inert gas.

20. The method according to claim 11 , wherein said raising the temperature of the sapphire substrate is performed in said atmosphere including the inert gas and hydrogen at said concentration of 10% or less relative to the inert gas.