Ba_3Si_6O_(12)N_2：Eu~(2＋)蛍光体の2波長励起フォトルミネッセンス評価

摘要

One candidate of efficient and reliable phosphor materials, Ba_3Si_6O_(12)N_2:Eu~(2+), is suitable for the combination with UV- to blue-LED, since it has efficient emission around 525 nm with a wide excitation band between 250 nm and 450 nm. Most phosphor materials, however, exhibit various trap levels in theromoluminescence spectra, and the relation between these trap levels and non-radiative recombination (NRR) centers is not clearly understood. Here we measured the Ba_3Si_6O_(12)N_2:Eu~(2+) phosphor by two-wavelength excited photoluminescence method which is effective for detecting NRR centers through non-contacting and nondestructive way. The method adds the second excitation light whose photon energy is lower than the bandgap, and observes the intensity change of photoluminescence. We observed an intensity increase with the addition of the BGE light, and obtained the first-step information on the presence of NRR centers by studying the BGE density and BGE energy dependence.%高効率、高信頼な蛍光体材料の探索が続けられている．ピーク波長525nmで，250nmから450nm付近での励起が可能なBa_3Si_6O_(12)N_2：Eu~(2+)（略称BSON）蛍光体は，紫外～青色LEDとの組み合わせに適した候補の一つである．その一方，BSONを含む蛍光体では，熱ルミネッセンス測定により種々のキャリア捕獲準位が観測され，非発光再結合準位との関連性には不明な点が多い。ここでは、非発光再結合準位として作用する禁制帯内準位の非破壊・非接触評価が可能な2波長励起フォトルミネセンス法を用いて，BSON蛍光体を評価した．バンドギャップより低いエネルギーを持つ禁制帯内励起（BGE）光の照射によりPL強度の増加を観測し，BGE光強度およびエネルギー依存性から，非発光再結合準位の存在に関する手掛かりが得られた．