NITRIDE SEMICONDUCTOR LIGHT EMITTING DEVICE
A nitride semiconductor light emitting device includes n-type and p-type nitride semiconductor layers, and an active layer disposed between the n-type and p-type nitride semiconductor layers and having a stack structure in which a plurality of quantum barrier layers and one or more quantum well layers are alternately stacked. A net polarization of the quantum barrier layer is smaller than or equal to a net polarization of the quantum well layer. A nitride semiconductor light emitting device can be provided, which can realize high efficiency even at high currents by minimizing the net polarization mismatch between the quantum barrier layer and the quantum well layer. Also, a high-efficiency nitride semiconductor light emitting device can be achieved by reducing the degree of energy-level bending of the quantum well layer.
1 . A nitride semiconductor light emitting device comprising:
n-type and p-type nitride semiconductor layers; and
an active layer disposed between the n-type and p-type nitride semiconductor layers and having a stack structure in which a plurality of quantum barrier layers and one or more quantum well layers are alternately stacked,
wherein a net polarization of the quantum barrier layer is smaller than or equal to a net polarization of the quantum well layer.
2 . The nitride semiconductor light emitting device of claim 1 , wherein a net polarization mismatch at an interface between the quantum barrier layer and the quantum well layer is smaller than a net polarization mismatch between GaN and In x Ga (1-x) N (0.15≦x≦0.25).
3 . The nitride semiconductor light emitting device of claim 2 , wherein the net polarization mismatch at the interface between the quantum barrier layer and the quantum well layer is smaller than half the net polarization mismatch between GaN and In x Ga (1-x) N (0.15≦x≦0.25).
4 . The nitride semiconductor light emitting device of claim 1 , wherein a net polarization mismatch at an interface between the quantum barrier layer and the quantum well layer is smaller than a net polarization mismatch between GaN and In x Ga (1-x) N (0.3≦x≦0.4).
5 . The nitride semiconductor light emitting device of claim 4 , wherein the net polarization mismatch at the interface between the quantum barrier layer and the quantum well layer is smaller than half the net polarization mismatch between GaN and In x Ga (1-x) N (0.3≦x≦0.4).
6 . The nitride semiconductor light emitting device of claim 1 , wherein a net polarization mismatch at an interface between the quantum barrier layer and the quantum well layer is smaller than a net polarization mismatch between GaN and In x Ga (1-x) N (0≦x≦0.1).
7 . The nitride semiconductor light emitting device of claim 6 , wherein the net polarization mismatch at the interface between the quantum barrier layer and the quantum well layer is smaller than half the net polarization mismatch between GaN and In x Ga (1-x) N (0≦x≦0.1).
8 . The nitride semiconductor light emitting device of claim 1 , wherein a quantum barrier layer and a quantum well layer adjacent to each other in the active layer have the same net polarization.
9 . The nitride semiconductor light emitting device of claim 1 , wherein the quantum barrier layer has bandgap energy of the same magnitude as that of GaN.
10 . The nitride semiconductor light emitting device of claim 1 , wherein the quantum barrier layer has bandgap energy which is smaller than that of GaN and greater than that of In 0.2 Ga 0.8 N.
11 . The nitride semiconductor light emitting device of claim 1 , wherein a quantum barrier layer contacting the n-type nitride semiconductor layer among the plurality of quantum barrier layers has an n-type doped interface with the n-type nitride semiconductor layer.
12 . The nitride semiconductor light emitting device of claim 11 , wherein the interface of the quantum barrier layer is Si delta-doped.
13 . The nitride semiconductor light emitting device of claim 1 , wherein a quantum barrier layer contacting the p-type nitride semiconductor layer among the plurality of quantum barrier layers has a p-type doped interface with the p-type nitride semiconductor layer.
14 . The nitride semiconductor light emitting device of claim 13 , wherein the interface of the quantum barrier layer is Mg delta-doped.
15 . The nitride semiconductor light emitting device of claim 1 , further comprising an electron blocking layer disposed between the active layer and the p-type nitride semiconductor layer.
16 . The nitride semiconductor light emitting device of claim 1 , further comprising a substrate for growth contacting the n-type nitride semiconductor layer,
wherein the n-type nitride semiconductor layer is disposed on a polar surface of the substrate.
17 . The nitride semiconductor light emitting device of claim 16 , wherein the n-type nitride semiconductor layer is disposed on a C (0001) plane of a sapphire substrate.
18 . The nitride semiconductor light emitting device of claim 1 , wherein at least one of the plurality of quantum barrier layers has a superlattice structure.
19 . The nitride semiconductor light emitting device of claim 18 , wherein the quantum barrier layer having the superlattice structure has a structure in which first and second layers respectively formed of In 0.1 Ga 0.9 N and GaN are alternately stacked.
20 . A nitride semiconductor light emitting device comprising:
n-type and p-type nitride semiconductor layers; and
an active layer disposed between the n-type and p-type nitride semiconductor layers and having a structure in which a plurality of quantum barrier layers and one or more quantum well layers are alternately stacked,
wherein at least one of the quantum well layers has a constant energy level of a conduction band.