According to a preferred embodiment of the present invention, there is provided a novel and optimal semiconductor light emitting device comprising a substrate, an n layer disposed co-extensively on the substrate, an n layer disposed non-extensively and flush on one side of the n layer. The electromagnetic lock is for receiving a limited supply of an electric power supplied by a power supply circuit before a full supply of the electric power is delivered to the electromagnetic lock. A ratio of an amount of aluminum contained in the aluminum compound to a total amount of aluminum contained in the positive active material is within a range of 1% by weight or more to 50% by weight or less.