Non-polar nitride-based light emitting device and method for fabricating the same

1. A non-polar nitride-based light emitting device comprising:

a substrate including r-plane sapphire;

a semiconductor structure including a first-type semiconductor layer on the substrate, an active layer on the first-type semiconductor layer and a second-type semiconductor layer on the active layer, wherein the semiconductor structure comprises a-plane nitride semiconductor;

a light extraction layer including a-plane nitride semiconductor on a surface of the semiconductor structure, wherein the light extraction layer comprises at least one layer including indium, the light extraction layer includes a plurality of unit structures having an inverted pyramidal intaglio shape, and wherein the unit structure has a lowest point where dislocation in the second-type semiconductor layer meets the light extraction layer;

an overdoped second-type semiconductor layer having higher doping concentration than that of the second-type semiconductor layer on the light extraction layer, wherein a lowest portion of the unit structure is located between the surface of the semiconductor structure and the overdoped second-type semiconductor layer;

a first electrode electrically connected to the first-type semiconductor layer; and

a second electrode electrically connected to the second-type semiconductor layer.

2. The non-polar nitride-based light emitting device according to claim 1 , wherein the inverted pyramidal intaglio shape is a pyramidal shape having a virtual base plane having a quadrangular shape.

3. The non-polar nitride-based light emitting device according to claim 2 , wherein the virtual base plane has a lozenge shape or a diamond shape.

4. The non-polar nitride-based light emitting device according to claim 3 , wherein the lozenge shape or the diamond shape is configured to be asymmetrical such that the length of two sides and the length of other two sides opposite the two sides are different.

5. The non-polar nitride-based light emitting device according to claim 1 , wherein the light extraction layer has a structure in which at least one first layer and at least one second layer are alternately stacked.

6. The non-polar nitride-based light emitting device according to claim 5 , wherein the at least one first layer comprises an InGaN layer and the at least one second layer comprises a GaN layer.

7. The non-polar nitride-based light emitting device according to claim 1 , further comprising a transparent conductive layer on the light extraction layer.

8. The non-polar nitride based light emitting device according to claim 1 , wherein the unit structure connects a dislocation in the semiconductor structure.

9. A non-polar nitride-based light emitting device comprising:

a substrate including r-plane sapphire;

a semiconductor structure including a first-type semiconductor layer on the substrate, an active layer on the first-type semiconductor layer and a second-type semiconductor layer formed on the active layer;

a light extraction structure including a plurality of first unit structures having an inverted pyramidal intaglio shape and a plurality of second unit structures located between the plurality of first unit structures, the second unit structure having an inverted pyramidal intaglio shape and a size smaller than the plurality of first unit structures, wherein the light extraction structure comprises at least one layer that includes indium,

wherein the light extraction structure is provided on a light extraction layer,

wherein at least one of the first-type semiconductor layer, the second-type semiconductor layer, or the active layer includes a-plane nitride semiconductor, and

wherein a lowest portion of the first unit structure is located at a top surface of the semiconductor structure, wherein the first unit structure connects a dislocation in the semiconductor structure;

an overdoped second-type semiconductor layer having higher doping concentration than that of the second-type semiconductor layer on the light extraction layer;

a first electrode electrically connected to the first-type semiconductor layer; and

a second electrode electrically connected to the second-type semiconductor layer.

10. The non-polar nitride-based light emitting device according to claim 9 , wherein the inverted pyramidal intaglio shape is a pyramidal shape having a virtual base plane having a lozenge shape or a diamond shape.

11. The non-polar nitride-based light emitting device according to claim 9 , wherein the light extraction layer includes InGaN.

12. The non-polar nitride-based light emitting device according to claim 9 , wherein the light extraction layer has a structure in which at least one first layer and at least one second layer are alternately stacked.

13. The non-polar nitride-based light emitting device according to claim 12 , wherein the at least one first layer comprises a layer including InGaN and the at least one second layer comprises a layer including GaN.

14. The non-polar nitride-based light emitting device according to claim 9 , wherein a lowest portion of a first or second unit structure is located between the surface of the semiconductor structre and the overdoped second-type semiconductor layer.

15. A method for fabricating a non-polar nitride-based light emitting device comprising:

forming an a-plane semiconductor structure including a first-type semiconductor layer, an active layer and a second-type semiconductor layer on a r-plane sapphire substrate;

forming a light extraction layer including a material that is different from a material of the second-type semiconductor layer, wherein the light extraction layer comprises at least one layer including indium on a surface of the semiconductor structure, the light extraction layer forming a plurality of unit structures with an inverted pyramidal intaglio shape on the semiconductor structure such that the unit structure is formed at a top surface of the semiconductor structure, wherein the unit structure is started from dislocation in the second-type semiconductor layer;

forming an overdoped second-type semiconductor layer having higher doping concentration than that of the second-type semiconductor layer on the light extraction layer;

forming a transparent conductive layer on the overdoped second-type semiconductor layer;

forming a first electrode electrically connected to the first-type semiconductor layer; and

forming a second electrode on the transparent conductive layer.

16. The method according to claim 15 , wherein the light extraction layer has a structure in which at least one first layer including InGaN and at least one second layer including GaN are alternately stacked.

17. The method according to claim 16 , wherein at least two pairs of the at least one first layer and the at least one second layer are alternately stacked.

18. The method according to claim 15 , wherein the formation of the light extraction layer is carried out in a condition that a growth velocity in the vertical direction is higher than a growth velocity in the horizontal direction.

19. The method according to claim 15 , wherein the unit structure connects a dislocation in the semiconductor structure.