To improve semiconductor-based systems for generating white light, a phosphor is integrated into a reflective material of an external structure. A disclosed exemplary system, for luminance or illumination applications, utilizes an energy source package, for emitting radiant energy of a first wavelength. The package typically contains an LED or other semiconductor device. A reflector outside the package has a reflective surface arranged to receive radiant energy from the energy source. At least some of the received radiant energy of the first wavelength excites one or more phosphors doped within the reflector to emit visible light, including visible light energy of at least one second wavelength different from the first wavelength. At least some of visible light emitted by the phosphor is reflected by the reflective surface of the reflector and directed to facilitate the particular humanly perceptible luminance or illumination application.