A light-emitting device includes a substrate, an n-type semiconductor layer, an active layer, and a p-type semiconductor layer; wherein the active layer is a multi-quantum-well (MQW) active layer with a predetermined n-type doping profile. More specifically, the MQW active layer is doped with n-type dopants in the region near the p-type semiconductor layer and the n-type semiconductor layer, and the central region is not doped with the n-type dopants.