Light emitting device and light emitting device package

A light emitting device comprising:

• a first conduction type semiconductor layer;
• an active layer formed on the first conduction type semiconductor layer;
• and
• a second conduction type semiconductor layer formed on the active layer,
• wherein the active layer includes a plurality of quantum well layers and a plurality of quantum barrier layers, a face direction lattice constant of the first conduction type semiconductor layer or the second conduction type semiconductor layer is greater than each of face direction lattice constants of the quantum barrier layers, and the face direction lattice constant of the first conduction type semiconductor layer or the second conduction type semiconductor layer is smaller than each of the face direction lattice constants of the quantum well layers, and
• wherein each of the face direction lattice constants of the quantum well layers becomes greater gradually in a thickness direction from an edge to a middle of the respective quantum well layer.