THERMOACTIVATED SPECTROSCOPY OF HETEROVALENT IMPURITY TRAPS IN CDWO4

Recombination luminescence emission spectra, TSL and trap spectra esti mated by fractional glow technique (FGT), in nominally pure and Li-, B i- and He-doped CdWO4 crystals are reported. According to the investig ations by FGT heterovalent impurities Li, Bi and Ho causes localized e lectronic states which act as traps for charge carriers. It is shown t hat TSL results in emission of known blue-green luminescence band by e mptying of the Li+-related traps in CdWO4-Li and yellow luminescence b and by emptying of the Bi3+-related traps in CdWO4-Bi. It is proposed that blue-green and yellow luminescence occur by recombination corresp ondingly of free holes and free electrons at different intrinsic tungs tate group related luminescence centers.