Semiconductor scintillators ZnO and PbI2: Co-doping studies

It is known that the impurities In in CdS and Ga in ZnO act as donors to generate a population of electrons near the bottom of the conduction band. Fast luminescence is observed from these materials but the intensity of the luminescence is strongly dependent on the method used for dopant incorporation. Therefore, it is suspected that an additional dopant is responsible for trapping ionization holes and promoting rapid radiative recombination and these compete with native non-radiative centers. To verify this conjecture and to optimize the luminosity of this class of scintillators, we have been exploring the possibility of introducing dopants that act as efficient hole traps and radiative centers. In this work, we report on the luminosities and decay times of crystalline powders of ZnO doped with the donor Ga3+ and treated with H, doped with the acceptor N3− and with the isoelectronic hole trap S2−. Co-doped samples exhibit a large increase in luminosity and a fast mono-exponential decay. We also report on PbI2 doped with the donors Bi3+, La3+, and In3+ and co-doped with Ga3+ and P3−. PbI2 is dense (d=6.2 g/cm3) and is a candidate material for gamma-ray detection.