A window structure for a gallium nitride -based light emitting diode includes a Mg doped p window layer of a GaN compound; a thin, semi-transparent metal contact layer; and an amorphous current spreading layer formed on the contact layer. Two or more tubes in the radiant heat chemical reactor separate an exothermic heat source, such as flames and gas from a regenerative burner, from the endothermic reaction of the reactant gas occurring within the cavity of the refractory vessel. Accessories, including a wireless speaker, can be attached to the slide-on device with an attachment mechanism, including a hook-and-loop fastener.