NITRIDE SEMICONDUCTOR LIGHT EMITTING DEVICE
There is provided a nitride semiconductor light emitting device including an active layer having enhanced external quantum efficiency at both low and high current density. The nitride semiconductor light emitting device includes a first conductivity type nitride semiconductor layer; an active layer disposed on the first conductivity type nitride semiconductor layer and having a plurality of quantum well layers and at least one quantum barrier layer alternately arranged; and a second conductivity type nitride semiconductor layer disposed on the active layer. The plurality of quantum well layers disposed adjacent to each other include first and second quantum well layers having different thicknesses.
1 . A nitride semiconductor light emitting device comprising:
a first conductivity type nitride semiconductor layer;
an active layer disposed on the first conductivity type nitride semiconductor layer and having a plurality of quantum well layers and at least one quantum barrier layer alternately arranged; and
a second conductivity type nitride semiconductor layer disposed on the active layer,
wherein the plurality of quantum well layers disposed adjacent to each other include first and second quantum well layers having different thicknesses.
2 . The nitride semiconductor light emitting device of claim 1 , wherein the first and second quantum well layers emit light of the same wavelength.
3 . The nitride semiconductor light emitting device of claim 2 , wherein the first quantum well layer has an In composition ratio lower than the second quantum well layer.
4 . The nitride semiconductor light emitting device of claim 1 , wherein the first quantum well layer is disposed adjacent to the first conductivity type nitride semiconductor layer, and the second quantum well layer is disposed adjacent to the second conductivity type nitride semiconductor layer and has a thickness thinner than the first quantum well layer.
5 . The nitride semiconductor light emitting device of claim 4 , wherein the first conductivity type nitride semiconductor layer is an n-type nitride semiconductor layer.
6 . The nitride semiconductor light emitting device of claim 1 , wherein the first quantum well layer has a thickness of 2 nm to 15 nm.
7 . The nitride semiconductor light emitting device of claim 1 , wherein the second quantum well layer has a thickness of 1 nm to 4 nm.
8 . The nitride semiconductor light emitting device of claim 1 , wherein at least one of the first and second quantum well layers has an energy band structure including inclined portions.
9 . The nitride semiconductor light emitting device of claim 8 , wherein the energy band structure includes inclined portions having any one of triangular-shaped and trapezoidal-shaped structures.
10 . The nitride semiconductor light emitting device of claim 1 , wherein the active layer has one or more sets, each including the first and second quantum well layers and a first quantum barrier layer disposed therebetween and includes a second quantum barrier layer dividing the sets.
11 . The nitride semiconductor light emitting device of claim 10 , wherein the first and second quantum barrier layers have the same thickness.
12 . The nitride semiconductor light emitting device of claim 10 , wherein the second quantum barrier layer has a thickness greater than the first quantum barrier layer.