A light emitting diode, comprising: a substrate; a first light emitting cell and a second light emitting cell disposed adjacent to each other on the substrate and each comprising an n-type semiconductor layer, a p-type semiconductor layer, and an active layer disposed between the n-type semiconductor layer and the p-type semiconductor layer; reflection structures disposed on the p-type semiconductor layers of the first light emitting cell and the second light emitting cell, respectively, and contacting the p-type semiconductor layers; a first contact layer in ohmic contact with the n-type semiconductor layer of the first light emitting cell; a second contact layer in ohmic contact with the n-type semiconductor layer of the second light emitting cell and connected to the reflection structure on the first light emitting cell; an n-electrode pad disposed over the first light emitting cell and electrically connected to the first contact layer; and a p-electrode pad disposed over the second light emitting cell and electrically connected to the reflection structure on the second light emitting cell, wherein the first light emitting cell and the second light emitting cell are isolated from each other by an isolation region exposing the substrate, wherein the n-type semiconductor layers of the first light emitting cell and the second light emitting cell comprise inner side surfaces facing each other and outer side surfaces exposed to outside, wherein the at least one outer side surface is inclined steeper than the inner sides, wherein each of the first light emitting cell and the second light emitting cell comprises a mesa disposed on a partial region of the n-type semiconductor layer, and comprising the active layer and the p-type semiconductor layer, characterised in that each of the first contact layer and the second contact layer is in contact with the n-type semiconductor layer in a region between the outer side surfaces of the n-type semiconductor layer and the mesa along a periphery of the mesa, wherein each of the mesas has a through-hole exposing the n-type semiconductor layer through the p-type semiconductor layer and the active layer, and each of the first contact layer and the second contact layer further contacts the n-type semiconductor layer through the through-hole of the mesa. a substrate; a first light emitting cell and a second light emitting cell disposed adjacent to each other on the substrate and each comprising an n-type semiconductor layer, a p-type semiconductor layer, and an active layer disposed between the n-type semiconductor layer and the p-type semiconductor layer; reflection structures disposed on the p-type semiconductor layers of the first light emitting cell and the second light emitting cell, respectively, and contacting the p-type semiconductor layers; a first contact layer in ohmic contact with the n-type semiconductor layer of the first light emitting cell; a second contact layer in ohmic contact with the n-type semiconductor layer of the second light emitting cell and connected to the reflection structure on the first light emitting cell; an n-electrode pad disposed over the first light emitting cell and electrically connected to the first contact layer; and a p-electrode pad disposed over the second light emitting cell and electrically connected to the reflection structure on the second light emitting cell, wherein the first light emitting cell and the second light emitting cell are isolated from each other by an isolation region exposing the substrate, wherein the n-type semiconductor layers of the first light emitting cell and the second light emitting cell comprise inner side surfaces facing each other and outer side surfaces exposed to outside, wherein the at least one outer side surface is inclined steeper than the inner sides, wherein each of the first light emitting cell and the second light emitting cell comprises a mesa disposed on a partial region of the n-type semiconductor layer, and comprising the active layer and the p-type semiconductor layer, characterised in that each of the first contact layer and the second contact layer is in contact with the n-type semiconductor layer in a region between the outer side surfaces of the n-type semiconductor layer and the mesa along a periphery of the mesa, wherein each of the mesas has a through-hole exposing the n-type semiconductor layer through the p-type semiconductor layer and the active layer, and each of the first contact layer and the second contact layer further contacts the n-type semiconductor layer through the through-hole of the mesa.