a light - emitting apparatus composed of a light source that emits primary light and a phosphor that absorbs the primary light and emits secondary light offers high brightness , low power consumption , and a long lifetime while minimizing adverse effects on the environment . the phosphor is formed of a iii - v group semiconductor in the form of fine - particle crystals each having a volume of 2 800 nm 3 or less . the light emitted from the fine - particle crystals depends on their volume , and therefore giving the fine - particle crystals a predetermined volume distribution makes it possible to adjust the wavelength range of the secondary light .