US Patent 10156335 Light-emitting device

A light-emitting device comprises a semiconductor structure comprising a first conductivity-type semiconductor layer, a second conductivity-type semiconductor layer, a first intermediate layer, a second intermediate layer, and an active region capable of emitting radiation, wherein the active region is between the first intermediate layer and the second intermediate layer, the first intermediate layer is in direct contact with the first conductivity-type semiconductor layer, the second intermediate layer is in direct contact with the second conductivity-type semiconductor layer, and the active region comprises alternated well layers and barrier layers, wherein each barrier layer has a thickness; wherein a first difference between a refractive index of the first intermediate layer and a refractive index of the first conductivity-type semiconductor layer is less than a second difference between a refractive index of the second intermediate layer and a refractive index of the second conductivity-type semiconductor layer.