Group III nitride semiconductor device and light-emitting device using the same

1. A Group III nitride semiconductor device comprising:

a sapphire substrate; and

a plurality of Group III nitride semiconductor layers provided on the substrate,

wherein a first layer which is in contact with the substrate is composed of silicon-doped Al x Ga 1-x N (0<x≦1) and has a structure formed of aggregated columnar crystal grains having a width of 10 to 50 nm.

2. A Group III nitride semiconductor device according to claim 1 , wherein the first layer contains silicon in an amount of 1×10 16 to 1×10 19 atoms/cm 3 .

3. A Group III nitride semiconductor device comprising:

a substrate; and

a plurality of Group III nitride semiconductor layers provided on the substrate, including a first layer which is in contact with the substrate and a second layer grown on said first layer,

wherein said first layer which is in contact with the substrate is composed of Al x Ga 1-x N (0≦x≦1), and the difference in height between a protrusion and a depression which are present at the interface between the first layer and the second layer is 10 nm or more and is equal to, or less than, 99% the thickness of the first layer.

4. A Group III nitride semiconductor device according to claim 1 , wherein the first layer has a thickness of 20 nm to 200 nm.

5. A Group III nitride semiconductor light-emitting device comprising:

a substrate;

an n-type layer, a light-emitting layer, and a p-type layer, which are composed of a Group III nitride semiconductor single crystal and are provided on the substrate in this order;

a negative electrode provided on the n-type layer; and

a positive electrode provided on the p-type layer,

wherein there is a layer composed of silicon-doped Al x Ga 1-x N (0<x≦1) in contact with the substrate and the layer in contact with the substrate has a structure formed of aggregated columnar crystal grains having a width of 10 to 50 nm.

6. A method for producing a Group III nitride semiconductor device comprising a sapphire substrate, and a plurality of Group III nitride semiconductor layers provided on the substrate, wherein a first layer which is in contact with the substrate is composed of silicon-doped Al x Ga 1-x N (0<x<1) and has a structure formed of aggregated columnar crystal grains having a width of 10 to 50 nm, which method comprises a first step of depositing, on the surface of the substrate, a layer containing fine Group III metal particles containing silicon; a second step of nitridizing the fine particles in an atmosphere containing a nitrogen source; and a third step of growing a Group III nitride semiconductor single crystal on the thus-nitridized fine particles.

7. A method for producing a Group III nitride semiconductor device according to claim 6 , which further comprises, between the first and second steps, an annealing step of heating the fine particles in an atmosphere containing hydrogen gas and/or nitrogen gas.

8. A Group III nitride semiconductor device according to claim 1 , wherein the first layer is composed of silicon-doped Al x Ga 1-x N (0<x<1).

9. A Group III nitride semiconductor light-emitting device according to claim 5 , wherein the layer in contact with the substrate is composed of silicon-doped Al x Ga 1-x N (0<x<1).

10. A Group III nitride semiconductor device according to claim 1 , wherein the columnar crystal grains have a width of 20 to 40 nm.

11. A Group III nitride semiconductor device according to claim 1 , wherein the first layer is a continuous layer formed by a continuous formation of the columnar crystal grains.

12. A Group III nitride semiconductor device according to claim 3 , wherein the thickness of the first layer is a thickness of a thickest portion of the first layer which has a maximum height of the first layer.

13. A Group III nitride semiconductor device according to claim 3 , wherein the difference in height between the protrusion and the depression is a maximum height difference between a maximum protrusion and a maximum depression of an upper surface of the first layer.

14. A Group III nitride semiconductor device according to claim 13 , wherein the maximum protrusion and the maximum depression of the upper surface of the first layer is a thickest portion and a least thickest portion of the first layer, respectively.

15. A Group III nitride semiconductor device according to claim 14 , wherein the thickness of the first layer is the thickest portion of the first layer having a maximum height.

16. A Group III nitride semiconductor device according to claim 14 , wherein the difference in height between the protrusion and the depression is 40 nm or less.

17. A Group III nitride semiconductor device according to claim 14 , wherein the columnar crystal grains have a width of 20 to 40 nm.

18. A Group III nitride semiconductor device according to claim 3 , wherein the difference in height between the protrusion and the depression is 10 nm or more and is equal to, or less than, 90% the thickness of the first layer.

19. A Group III nitride semiconductor device according to claim 3 , wherein the difference in height between the protrusion and the depression is 60 nm or less.

20. A Group III nitride semiconductor device according to claim 3 , wherein the difference in height between the protrusion and the depression is 40 nm or less.