White light emitting diodes

Using blue-emitting GaN LEDs on SiC substrate chips, as primary light sources, we have fabricated green, yellow, red and white light emitting diodes (LUC0LEDs). The generation of mixed colors,as turquoise and magenta, in also demonstrated. The underlying physical principle in that of luminescence down-conversion (Stoke& shift), as typical for organic dye molecules and many inorganic phosphors. For white light generation via the LUCOLED principle, the phosphor Y3Al5O12:Ce(3+)(4f1) is ideally suited. The optical characteristics of Ce(3+)(4f1) in Y3Al5O12 (YAG) are discussed in detail. Possibilities to "tune" the white color by various substitutions in the garnet lattice are shortly outlined.