The present invention comprises a substrate, and at least one serial array having a plurality of light emitting cells connected in series on the substrate. Each of the light emitting cells comprises a lower semiconductor layer, an upper semiconductor layer, an active layer interposed between the lower and upper semiconductor layers, a lower electrode formed on the lower semiconductor layer exposed at a first corner of the substrate, an upper electrode layer formed on the upper semiconductor layer, and an upper electrode pad formed on the upper electrode layer exposed at a second corner of the substrate. The upper electrode pad and the lower electrode are respectively disposed at the corners diagonally opposite to each other, and are symmetric with respect to those of adjacent another of the light emitting cells.