Material layer stack, light emitting element, light emitting package, and method of fabricating light emitting element

1. A material layer stack comprising:

a substrate having a first lattice constant; and

a semiconductor layer on the substrate, the semiconductor layer having a second lattice constant that is different from the first lattice constant,

wherein the semiconductor layer comprises:

a first impurity layer having a first impurity concentration;

a second impurity layer having a second impurity concentration that is greater than the first impurity concentration; and

a third impurity layer having a third impurity concentration that is greater than the second impurity concentration,

wherein impurities comprised in the first impurity layer, the second impurity layer, and the third impurity layer have the same conductivity type, and

wherein a thickness of the second impurity layer is about 0.8 times to about 1.2 times a thickness of the first impurity layer.

2. The material layer stack according to claim 1 , wherein, among the first impurity layer, the second impurity layer, and the third impurity layer, the first impurity layer is disposed to be closest to the substrate, and the third impurity layer is disposed to be farthest away from the substrate.

3. The material layer stack according to claim 2 , wherein the impurities comprised in the first impurity layer, the second impurity layer, and the third impurity layer have an n-type conductivity.

4. The material layer stack according to claim 2 , wherein the first impurity concentration, the second impurity concentration, and the third impurity concentration change discretely at interfaces of the impurity layers.

5. The material layer stack according to claim 1 , wherein a thickness of the third impurity layer is about 1.8 times to about 2.2 times the thickness of the first impurity layer.

6. The material layer stack according to claim 2 , wherein the impurities are silicon (Si) or carbon (C).

7. The material layer stack according to claim 6 , wherein the first impurity layer has an impurity concentration of about 1.0×10 17 cm −3 to about 2.0×10 18 cm −3 .

8. The material layer stack according to claim 6 , wherein the second impurity layer has an impurity concentration of about 5.0×10 17 cm −3 to about 5.0×10 18 cm −3 .

9. The material layer stack according to claim 6 , wherein the third impurity layer has an impurity concentration of about 5.0×10 18 cm −3 to about 2.0×10 19 cm −3 .

10. A light emitting element comprising:

a first conductivity type semiconductor layer and a second conductivity type semiconductor layer connected to respective electrodes; and

an active layer configured to generate light using power supplied through the electrodes,

wherein the first conductivity type semiconductor layer comprises a plurality of impurity layers having different thicknesses and different impurity concentrations such that an impurity layer disposed to be farthest from the active layer has a lowest thickness and a lowest impurity concentration among the impurity layers.

11. The light emitting element of claim 10 , wherein an impurity layer disposed to be closest to the active layer is a greatest thickness and has a highest impurity concentration among the impurity layers.

12. The light emitting element of claim 10 , wherein the plurality of impurity layers are stacked such that a thickness and an impurity concentration increase by layer in proportion to a distance from a bottom of the first conductivity type semiconductor layer toward the active layer.

13. The light emitting element of claim 12 , wherein the impurity concentration changes substantially discontinuously at interfaces of the impurity layers.

14. The light emitting element of claim 12 , wherein the impurity concentration changes such that a rate of continuous change in the impurity concentration at an interface between two impurity layers disposed to be closest to the active layer is greater than that at an interface between two impurity layers disposed to be farthest from the active layer among the impurity layers.

15. The light emitting element of claim 12 , wherein a thickness and an impurity concentration of an impurity layer disposed between top and bottom impurity layers among the impurity layers are greater than those of the impurity layer disposed to be farthest from the active layer and less than those of an impurity layer disposed to be closest to the active layer among the impurity layers.

16. The light emitting element of claim 10 , wherein the impurity concentration of each of the plurality of impurity layers is constant within the each layer such that an impurity concentration at an arbitrary height in the each layer ranges within ±10% of an average impurity concentration of the each layer.

17. The light emitting element of claim 10 , wherein the impurity layer disposed to be farthest from the active layer has a highest surface crystallinity and surface uniformity among the impurity layers.

18. A light emitting element comprising:

a substrate;

a first conductivity type semiconductor layer;

a second conductivity type semiconductor layer; and

an active layer interposed between the first conductivity type semiconductor layer and the second conductivity type semiconductor layer,

wherein the first conductivity type semiconductor layer comprises a first impurity layer, a second impurity layer, and a third impurity layer in series,

wherein respective impurity concentrations of the first impurity layer, the second impurity layer, and the third impurity layer sequentially increase from the first impurity layer to the third impurity layer, and

wherein impurity concentrations change at interfaces between the first impurity layer, the second impurity layer, and the third impurity layer, and

wherein the first conductivity type semiconductor layer is interposed between the substrate and the second conductivity type semiconductor layer.

19. A light emitting package comprising:

a light emitting element mounted on a package substrate;

a connector electrically connecting the package substrate to the light emitting element; and

a molding unit molding the light emitting element,

wherein the light emitting element is the light emitting element according to claim 10 .

20. The light emitting element according to claim 18 , wherein a thickness of the second impurity layer is about 0.8 times to about 1.2 times a thickness of the first impurity layer.