Light emitting device and light unit having same

A light emitting device comprising:

• a plurality of superlattice layers;
• a first conductive semiconductor layer on the plurality of superlattice layers;
• an active layer that is disposed on the first conductive semiconductor layer and has a plurality of barrier layers and a plurality of well layers;
• and
• a second conductive semiconductor layer which is disposed on the active layer,
• wherein the plurality of superlattice layers include at least three superlattice layers,
• wherein each of the at least three superlattice layers has a plurality of pairs of at least a first layer and a second layer,
• wherein difference in composition of an aluminum between the first layer and the second layer of a superlattice layer adjacent to the active layer becomes greater than difference in composition of an aluminum between the first layer and the second layer of another superlattice layer in the superlattice layers,
• wherein a thickness of the first layer of the superlattice layer adjacent to the active layer is greater than a thickness of the first layer of another superlattice layer in the superlattice layers,
• wherein the second layer is disposed on the first layer in each of the superlattice layers,
• wherein the first layer of each of the at least three superlattice layers have a different thickness from each other,
• wherein the plurality of superlattice layers include a first superlattice layer, a second superlattice layer on the first superlattice layer, a third superlattice layer on the second superlattice layer, and a fourth superlattice layer between the third superlattice layer and the first conductive semiconductor layer, and
• wherein the pair of the first layer/the second layer of each of the first to fourth superlattice layers includes a pair of AlGaN/AlN.

A lighting unit comprising:

• a body which has a cavity;
• a light emitting device disposed in the cavity, the light emitting device comprising:
• a plurality of superlattice layers;
• a first conductive semiconductor layer on the plurality of superlattice layers;
• an active layer that is disposed on the first conductive semiconductor layer and has a plurality of barrier layers and a plurality of well layers;
• and
• a second conductive semiconductor layer which is disposed on the active layer,
• wherein the plurality of superlattice layers include at least three superlattice layers,
• wherein each of the at least three superlattice layers has a plurality of pairs of at least a first layer and a second layer,
• wherein a composition of aluminum in the first layer of a superlattice layer becomes smaller, as the superlattice layer among the at least three superlattice layers becomes one which is positioned to be adjacent to the active layer,
• wherein each of the at least three superlattice layers has the same composition of aluminum in the second layer,
• wherein the second layer is disposed on the first layer in each of the superlattice layers,
• wherein the first conductive semiconductor layer contacts the second layer of the superlattice layer which is positioned to be adjacent to the active layer, and
• wherein the plurality of superlattice layers include a first superlattice layer, a second superlattice layer on the first superlattice layer, a third superlattice layer on the second superlattice layer, and a fourth superlattice layer between the third superlattice layer and the first conductive semiconductor layer;
• a transparent window which is disposed within the cavity;
• and
• a moisture-proof film which is disposed on the transparent window and the body.