Interpretation of thermoluminescence and thermally stimulated conductivity experiments: Part II: Application to CdGa 2S 4

Abstract

Results of thermally stimulated luminescence (TSL) and conductivity (TSC) experiments on CdGa 2S 4 are reported. In the lower temperature region of the TSl curve a decay of luminescence is observed that is probably due to donor-acceptor pair recombination since no accompanying conduction is measured. The TSL and TSC curves of the undoped material further consist essentially of two peaks. If trap depths are calculated with various methods from the literature it turns out that for one peak different values are obtained. These differences cannot be explained with the conventional model consisting of one trapping level and one recombination level. If the results are compared with more complex models it follows that thermal quenching, the presence of a trap distribution, thermally disconnected traps and recombination via excited states, are important. This is most clearly demonstrated in the cases with excess Ga and with Ag or In as dopant. Although this approach probably yields valuable information about CdGa 2S 4, no definite conclusions may be drawn since some essential questions remain unsolved.