A light emitting device includes a stacked structure and a first insulating layer covering at least side surfaces of the stacked structure including a p-type and n-type semiconductor layers, a light emitting layer sandwiched between the p-type and n-type semiconductor layers, an n-type electrode on the n-type semiconductor layer, an n-type contact layer sandwiched between the n-type semiconductor layer and the n-type electrode, a p-type electrode on the p-type semiconductor layer, an n-type contact pad on the n-type electrode, a p-type contact pad on the p-type electrode, and a semiconductor reflector between the light emitting layer and the n-type contact layer including multiple periods, each period including at least a first layer and at least a second layer having a refractive index different from a refractive index of the first layer. The light emitting device could be applied to wide color gamut (WCG) backlight modules or ultra-thin backlight modules.