Semiconductor light emitting element and method for manufacturing the same

1. A semiconductor light emitting element, comprising:

a first semiconductor layer of an n-type including a nitride semiconductor;

a second semiconductor layer of a p-type including a nitride semiconductor; and

a light emitting unit provided between the first semiconductor layer and the second semiconductor layer, the light emitting unit including a plurality of well layers stacked alternately with a plurality of barrier layers,

the well layers including a first p-side well layer most proximal to the second semiconductor layer, and a second p-side well layer second most proximal to the second semiconductor layer,

a localization energy of excitons of the first p-side well layer being smaller than a localization energy of excitons of the second p-side well layer.

2. The element according to claim 1 , wherein a thickness of the first p-side well layer is not less than 3 nanometers and not more than 6 nanometers, and a thickness of the second p-side well layer is not less than 3 nanometers and not more than 6 nanometers.

3. The element according to claim 1 , wherein the localization energy of excitons of the first p-side well layer is less than 30 milli-electron volts.

4. The element according to claim 1 , wherein the localization energy of excitons of the second p-side well layer is not less than 50 milli-electron volts.

5. The element according to claim 1 , wherein the localization energy of excitons of the second p-side well layer is not less than 40 milli-electron volts.

6. The element according to claim 1 , wherein the localization energy of excitons of the second p-side well layer is not less than 30 milli-electron volts.

7. The element according to claim 1 , wherein the localization energy of excitons of the first p-side well layer is less than 40 milli-electron volts.

8. The element according to claim 1 , wherein the localization energy of excitons of the first p-side well layer is less than 50 milli-electron volts.

9. The element according to claim 1 , wherein fluctuation of an In concentration of the second p-side well layer is higher than fluctuation of an In concentration of the first p-side well layer.

10. The element according to claim 1 , wherein fluctuation in a plane of the second p-side well layer of a thickness of the second p-side well layer is higher than fluctuation in a plane of the first p-side well layer of the thickness of the first p-side well layer.

11. The element according to claim 1 , wherein the localization energy of excitons of the well layers decreases from the first semiconductor layer side toward the second semiconductor layer side.

12. The element according to claim 1 , wherein a growth rate of the second p-side well layer is lower than a growth rate of the first p-side well layer.

13. A method for manufacturing a semiconductor light emitting element, comprising:

forming a first semiconductor layer of an n-type including a nitride semiconductor;

forming a light emitting unit including a plurality of well layers and a plurality of barrier layers by alternately stacking the well layers with the barrier layers on the first semiconductor layer; and

forming a second semiconductor layer of a p-type including a nitride semiconductor on the light emitting unit,

the well layers including a first p-side well layer most proximal to the second semiconductor layer, and a second p-side well layer second most proximal to the second semiconductor layer,

a localization energy of excitons of the first p-side well layer being smaller than a localization energy of excitons of the second p-side well layer.

14. The method according to claim 13 , wherein a growth rate of the second p-side well layer is lower than a growth rate of the first p-side well layer.

15. The method according to claim 13 , wherein a growth rate of the second p-side well layer is not less than 0.1 times a growth rate of the first p-side well layer and not more than 0.5 times the growth rate of the first p-side well layer.

16. The method according to claim 13 , wherein a growth rate of the second p-side well layer is not less than 0.2 times a growth rate of the first p-side well layer and not more than 0.4 times the growth rate of the first p-side well layer.

17. The method according to claim 13 , wherein

the stacking of the well layers is performed by supplying a Group V element and a Group III element, and

a ratio of a supply amount of the Group V element to a supply amount of the Group III element in the forming of the second p-side well layer is higher than a ratio of the supply amount of the Group V element to a supply amount of the Group III element in the forming of the first p-side well layer.

18. The method according to claim 13 , wherein

the stacking of the well layers is performed by supplying a Group V element and a Group III element,

a supply amount of the Group V element in the forming of the second p-side well layer is same as a supply amount of the Group V element in the forming of the first p-side well layer, and

a supply amount of the Group III element in the forming of the second p-side well layer is less than a supply amount of the Group III element in the forming of the first p-side well layer.

19. The method according to claim 13 , wherein fluctuation of an In concentration of the second p-side well layer is higher than fluctuation of an In concentration of the first p-side well layer.

20. The method according to claim 13 , wherein fluctuation in a plane of the second p-side well layer of a thickness of the second p-side well layer is higher than fluctuation in a plane of the first p-side well layer of a thickness of the first p-side well layer.