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Energy spectra of the local states in the forbidden gap of monoclinic TlInS2xSe2(1-x) crystals

2004    Samedov, SR; Baykan, O; Gulubayov, A

Near IR properties of the mixed TllnS(2X)Se(2(l-x)) have been studied previously by the present authors. In this work the temperature and frequency dependence's of the conductivity and the current-voltage characteristics (in relatively weak electric field), have been investigated for monoclinic TlInS2XSe2(l-x) crystals, which are perspective materials for IR applications. From the temperature dependence's of conductivity in the direction perpendicular to c- axis the bandgap E-g = 2.22 eV was determined for beta-TlInS2 crystals. The impurity centres were determined located at 0.43, 0.73 eV and 0.35, 0,48, 1.12 eV for the direction of current i // c and i perpendicular to c, respectively. The concentration of the centres located at 0.48 and 1.12 eV were calculated to he N-A - N-D = 4.8 . 10(9) cm(-3) and 1.9 . 10(11) cm(-3), respectively. It was found that in the solid solutions TlInS2xSe2(l-x) for 0.3 less than or equal to x less than or equal to 1, the conductivity follows the dependence sigma (nu) = sigma(o).nu(s) in the temperature range between 100 to 600 K In the temperature range of 80 - 400 K charge bounce plays an important role in the conductivity mechanism. Occurrence of the deep and low-levels impurity centres and a "tail" of the density of energy states in TlInS2xSe2(l-x) crystals make them perspective for practical applications: switching and memory effects, N-type current-voltage characteristics, induced conductivity etc.