A light-emitting device comprising: a substrate having a first surface and a second surface, wherein the second surface is opposite to the first surface; a semiconductor structure formed on the first surface of the substrate, comprising a first type semiconductor layer, an active layer and a second type semiconductor layer; and an isolation region separating at least the active layer into a first part and a second part, wherein the first part is capable of generating the electromagnetic radiation, and the second part comprises a breakdown diode.