A semiconductor light-emitting device includes substrate, a plurality of light-emitting-element-layers of semiconductor material formed on the substrate so as to be isolated from each other and having a wider band gap than the substrate, and phosphors converting wavelengths of light from the light-emitting-element-layers into other wavelengths. The integral cathode includes an emitter made of a refractory metal such as tungsten, preferably doped with rhenium to afford malleability during construction and assembly. The customer profile may be based on data collected from the respective customer.