Disclosed is a light emitting device including a light emitting structure including a first conductive semiconductor layer, an active layer under the first conductive semiconductor layer, and a second conductive semiconductor layer under the active layer, a first electrode electrically connected with the first conductive semiconductor layer, a mirror layer under the light emitting structure, a window semiconductor layer between the mirror layer and the light emitting structure, a reflective layer under the mirror layer, a conductive contact layer between the reflective layer and the window semiconductor layer and in contact with the second conductive semiconductor layer, and a conductive support substrate under the reflective layer. The window semiconductor layer includes a C-doped P-based semiconductor doped with a higher dopant concentration. The conductive contact layer includes material different from that of the mirror layer with a thickness thinner than that of the window semiconductor layer.