This disclosure discloses a light-emitting device. The light-emitting device comprises: a substrate; an intermediate layer formed on the substrate; a transparent bonding layer; a first semiconductor window layer bonded to the semiconductor layer through the transparent bonding layer; and a light-emitting stack formed on the first semiconductor window layer. The intermediate layer has a refractive index between the refractive index of the substrate and the refractive index of the first semiconductor window layer.