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Trapping center parameters and optical absorption in. quaternary TI4In3GaS8, Tl4InGa3Se8,and Tl2InGaS4 semiconductors

We have carried out thermally stimulated current measurements on as-grown Tl(4)ln(3)GaS(8), Tl4InGa3Se8, and Tl2InGaS4 crystals in the low-temperature ranges of 10 - 90, 10 - 160, and 10 - 60 K, respectively. Using the different heating rates method, we revealed experimental evidence for trapping centers with activation energies of 12 meV (Tl4In3GaS8), 17 meV (Tl(4)lnGa(3)Se(8)), and 10 meV (Tl(2)lnGaS(4)). The capture cross sections of the traps were found to be 3.0 x 10(-25), 2.0 x 10(-26), and 1.3 x 10(-24) cm(2), respectively. The values of the activation energies were compared with those obtained in photoluminescence experiments. From an optical absorption study, the energies of the indirect band gaps were determined for the crystals studied.