The carrier capture and recombination processes in Ln/sup 3+/-activated scintillators

The ability of activator ions to capture charge carriers and assume a different charge state under ionizing radiation is essential for efficient performance of rare-earth (RE)-doped scintillator materials utilizing the carrier recombination energy. In this paper, the sequence of carrier trapping is discussed and interpreted using a simple, single-configuration-coordinate model for two different cases: In one case (LuPO/sub 4/:Ce, YAlO/sub 3/:Ce, LuAlO/sub 3/:Ce) the charge state involved in the scintillation mechanism is Ce/sup 4+/, while in the other (LuPO/sub 4/:Yb, YbPO/sub 4/) it is Yb/sup 2+/. The possibility of a nonradiative recombination via Ce and Yb ions is also considered and found highly unlikely in accordance with experimental results.