1. A semiconductor light emitting device, comprising: a first semiconductor layer; a second semiconductor layer on the first semiconductor layer; an active layer on the second semiconductor layer; a third semiconductor layer on the active layer; a fourth semiconductor layer on the third semiconductor layer; a first electrode layer connected to the first semiconductor layer; and a second electrode layer connected to the fourth semiconductor layer; wherein the first semiconductor layer has a composition equation of Al Y (Ga x In 1-x ) 1-Y N(0≦X,Y≦1), wherein the third semiconductor layer has a composition equation of Al Y (Ga x In 1-x ) 1-Y N(0≦X,Y≦1), wherein the active layer includes a plurality of quantum barrier layers and a plurality of quantum well layers having a material different from the quantum barrier layers, wherein the plurality of quantum well layers include an AlGaN based semiconductor layer, wherein the plurality of quantum barrier layers has a larger band gap energy than that of the quantum well layers, and wherein the second semiconductor layer has a thickness range of 1 nm to 500 nm and has a thickness thicker than that of the third semiconductor layer.