Light emitting device and lighting system
Disclosed are a light emitting device, a method of fabricating a light emitting device, a light emitting device package, and a lighting system. The light emitting device includes a first conductive semiconductor layer ( 112 ), an In x Ga 1-x N layer (where, 0<x≦1) ( 151 ) on the first conductive semiconductor layer ( 112 ), a GaN layer ( 152 ) on the In x Ga 1-x N layer ( 151 ), a first Al y1 Ga 1-y1 N layer (where, 0<y1≦1) ( 153 ) on the GaN layer ( 152 ), an active layer ( 114 ) on the first Al y1 Ga 1-y1 N layer ( 153 ), and a second conductive semiconductor layer ( 116 ) on the active layer ( 114 ).
1. A light emitting device comprising:
a first conductive semiconductor layer;
an In x Ga 1-x N layer (where, 0<x≦1) on the first conductive semiconductor layer;
a GaN layer on the In x Ga 1-x N layer;
a first Al y1 Ga 1-y1 N layer (where, 0<y1≦1) on the GaN layer;
an active layer on the first Al y1 Ga 1-y1 N layer;
a second conductive semiconductor layer on the active layer; and
a second Al y2 Ga 1-y2 N layer (where 0<y2≦1), interposed between between the first Al y1 Ga 1-y1 N layer and the active layer,
wherein the second Al y2 Ga 1-y2 N layer has bandgap energy higher than bandgap energy of the first Al y1 Ga 1-y1 N layer.
2. The light emitting device of claim 1 , wherein indium contained in the In x Ga 1-x N layer has concentration in a range of 2% to 15%.
3. The light emitting device of claim 1 , wherein the GaN layer has bandgap energy higher than bandgap energy of the In x Ga 1-x N layer.
4. The light emitting device of claim 1 , wherein the GaN layer has bandgap energy lower than bandgap energy of the first Al y1 Ga 1-y1 N layer.
5. The light emitting device of claim 1 , wherein the In x Ga 1-x N layer has bandgap energy higher than bandgap energy of a quantum well of the active layer.
6. The light emitting device of claim 1 , wherein the first Al y1 Ga 1-y1 N layer has bandgap energy higher than bandgap energy of a quantum barrier of the active layer.
7. The light emitting device of claim 1 , further comprising a second-concentration first conductive semiconductor layer interposed between the first conductive semiconductor layer and the In x Ga 1-x N layer.
8. The light emitting device of claim 7 , wherein the second-concentration first conductive semiconductor layer has bandgap energy higher than bandgap energy of the In x Ga 1-x N layer.
9. The light emitting device of claim 1 , further comprising a GaN-based superlattice layer interposed between the first Al y1 Ga 1-y N layer and the active layer.
10. The light emitting device of claim 9 , wherein the GaN-based superlattice layer has a bandgap energy level reduced in a direction from the first conductive semiconductor layer toward the active layer.
11. The light emitting device of claim 10 , wherein the GaN-based superlattice layer comprises a first-group GaN-based superlattice layer having first bandgap energy and a second-group GaN-based superlattice layer provided on the first conductive semiconductor layer and having second bandgap energy lower than the first bandgap energy.
12. The light emitting device of claim 11 , wherein a difference between first and second bandgap energy levels is equal to or higher than a photon energy level of the GaN-based superlattice layer.
13. The light emitting device of claim 11 , wherein the GaN-based superlattice layer further comprises a third-group GaN-based superlattice layer provided on the second-group GaN-based superlattice layer and having third bandgap energy.
14. The light emitting device of claim 11 , wherein the first-group GaN-based superlattice layer has a thickness thinner than a thickness of the second-group GaN-based superlattice layer.
15. A lighting system comprising a lighting unit including the light emitting device according to claim 1 .
16. A light emitting device comprising:
a first conductive semiconductor layer;
an In x Ga 1-x N layer (where, 0<x≦1) on the first conductive semiconductor layer;
a GaN layer on the In x Ga 1-x N layer;
a first Al y1 Ga 1-y1 N layer (where, 0<y1≦1) on the GaN layer;
a GaN-based superlattice layer on the first Al y1 Ga 1-y1 N layer, wherein the GaN-based superlattice layer comprises a first-group GaN-based superlattice layer having first bandgap energy and a second-group GaN-based superlattice layer provided on the first conductive semiconductor layer and having second bandgap energy lower than the first bandgap energy;
an active layer on the GaN-based superlattice layer; and
a second conductive semiconductor layer on the active layer,
wherein the GaN-based superlattice layer has a bandgap energy level reduced in a direction from the first conductive semiconductor layer toward the active layer, and
a difference between the first and second bandgap energy levels is equal to or higher than a photon energy level of the GaN-based superlattice layer.
17. The light emitting device of claim 16 , wherein the GaN-based superlattice layer further comprises a third-group GaN-based superlattice layer provided on the second-group GaN-based superlattice layer and having third bandgap energy.