Light emitting device, light emitting device package and lighting system including the same

A light emitting device comprising:

• a light emitting structure including a first conductive type semiconductor layer, an active layer under the first conductive type semiconductor layer, and a second conductive type semiconductor layer under the active layer;
• a first electrode on an upper side of the light emitting structure;
• a second electrode on an underside of the light emitting structure;
• at least one cavity penetrating the second conductive type semiconductor layer and the active layer;
• and
• an insulating layer disposed on the at least one cavity,
• wherein the second electrode comprises:
• a conductive layer;
• and
• a reflective layer disposed between the insulating layer and the conductive layer,
• wherein the insulating layer and the reflective layer fully fill the cavity, and wherein the reflective layer comprises at least one protrusion in the cavity,
• wherein the at least one protrusion comprises an upper portion and a lower portion having different sizes,
• wherein the first electrode is vertically aligned with the at least one protrusion,
• wherein a top surface of the reflective layer is higher than a top surface of the active layer in a portion vertically overlapping the first electrode, and
• wherein the top surface of the reflective layer comprises a flat top surface.