Patent ID: 8431945

Claim:
A light emitting device comprising: a light emitting structure that includes a first conductive semiconductor layer, an active layer on the first conductive semiconductor layer, and a second conductive semiconductor layer on the active layer; a light transmissive substrate disposed under the light emitting structure and having a refractive index that is less than a refractive index of the first conductive semiconductor layer; a mirror structure layer disposed under the light transmissive substrate and including a first mirror layer having a first refractive index and a second mirror layer having a second refractive index different from the first refractive index, wherein the first mirror layer and the second mirror layer are alternately stacked on each other; and a first electrode layer under the mirror structure layer, wherein the first mirror layer has a thickness of W·λ/(4·n 1 ·m), and the second mirror layer has a thickness of W·λ/(4·n 2 ·m) in which λ represents a wavelength of a light emitted from the light emitting structure, n 1 represents the first refractive index, n 2 represents the second refractive index, m represents a natural number, and W represents a weight constant in a range of about 1.05 to about 1.25.