Nitride semiconductor light-emitting chip, method of manufacture thereof, and semiconductor optical device

1. A nitride semiconductor light-emitting chip comprising:

a nitride semiconductor substrate having a principal growth plane; and

a nitride semiconductor layer grown on the principal growth plane of the nitride semiconductor substrate, wherein

the principal growth plane is a plane having off-angles in both a- and c-axis directions relative to an m plane, and

the off-angle in the a-axis direction is larger than the off-angle in the c-axis direction.

2. The nitride semiconductor light-emitting chip according to claim 1 , wherein

the off-angle in the a-axis direction and the off-angle in the c-axis direction are each larger than 0.1 degrees.

3. The nitride semiconductor light-emitting chip according to claim 1 , wherein

the off-angle in the a-axis direction is larger than 0.1 degrees but 10 degrees or smaller.

4. The nitride semiconductor light-emitting chip according to claim 3 , wherein

the off-angle in the a-axis direction is larger than 1 degree but 10 degrees or smaller.

5. The nitride semiconductor light-emitting chip according to claim 1 , wherein

the nitride semiconductor layer includes an active layer having a quantum well structure, and

the active layer has one well layer.

6. The nitride semiconductor light-emitting chip according to claim 1 , wherein

the nitride semiconductor layer includes an active layer having a quantum well structure, and

the active layer has two well layers.

7. The nitride semiconductor light-emitting chip according to claim 1 , wherein

the nitride semiconductor layer includes an active layer having a quantum well structure,

the active layer has a well layer formed of a nitride semiconductor containing In, and

an In composition ratio in the well layer is 0.15 or more but 0.45 or less.

8. The nitride semiconductor light-emitting chip according to claim 1 , wherein

the nitride semiconductor substrate is formed of GaN.

9. A semiconductor optical device comprising:

the nitride semiconductor light-emitting chip according to claim 1 ; and

a cap covering the nitride semiconductor light-emitting chip.

10. A method of manufacture of a nitride semiconductor light-emitting chip, the method comprising:

a step of preparing a nitride semiconductor substrate having as a principal growth plane a plane having off-angles in both a- and c-axis directions relative to an m plane, the off-angle in the a-axis direction being larger than the off-angle in the c-axis direction; and

a step of stacking, on the principal growth plane of the nitride semiconductor substrate, by an epitaxial growth method, a nitride semiconductor layer including an n-type semiconductor layer, an active layer, and a p-type semiconductor layer, wherein

the step of stacking the nitride semiconductor layer includes a step of forming, from a nitride semiconductor substrate side, the n-type semiconductor layer, the active layer, and the p-type semiconductor layer.

11. The method of manufacture of a nitride semiconductor light-emitting chip according to claim 10 , wherein

the step of stacking the nitride semiconductor layer includes a step of forming the p-type semiconductor layer at a growth temperature of 700° or higher but lower than 900° C.

12. The method of manufacture of a nitride semiconductor light-emitting chip according to claim 10 , wherein

the step of stacking the nitride semiconductor layer includes a step of forming the n-type semiconductor layer at a growth temperature of 900° or higher but lower than 1300° C.

13. The method of manufacture of a nitride semiconductor light-emitting chip according to claim 10 , wherein

the step of stacking the nitride semiconductor layer includes a step of forming the active layer at a growth temperature of 600° or higher but 770° C. or lower.