[14p-2K-1~17] 15.1 Bulk crystal growth

[14p-2K-4] Single Crystal Phosphors for High-Brightness White LEDs and LDs

〇Kiyoshi Shimamura^1,2, E.Garcia Villora¹, Stelian Arjoca^1,2, Daisuke Inomata³, Kazuo Aoki⁴ (1.NIMS, 2.Waseda Univ., 3.Tamura Corp., 4.KOHA Co., Ltd.)

Keywords:single crystal phosphor

White light-emitting diodes (WLEDs) are demanded for general lighting applications. The most economical WLED consists of a blue-LED and the yellow-phosphor Ce³⁺:Y₃Al₅O₁₂ (Ce:YAG) ceramic powders. However, in applications that require high-brightness (HB), a conventional packaging possesses several drawbacks. That is why, a new concept of high-brightness white LEDs based on Ce:YAG single crystal phosphor plates (SCPPs), which can overcome the conventional temperature- and photo-degradation problems, is proposed. SCPPs demonstrated excellent thermal stability with no temperature quenching, high values of luminous efficacy and increased quantum efficiency. 2 inch Ce:YAG single crystals were grown with different compositions by standard Czochralski technique. SCPPs prepared by the grown single crystals exhibited a very high internal quantum efficiency (QE_int) (over 95%), with an outstanding temperature stability in the temperature range 25-300^oC. In contrast with powder and ceramic phosphors, we found that the Ce³⁺ emission of Ce:YAG SCPPs practically does not depend on the Ce concentration.