Energy Spectra of the Local States in the Forbidden Gap of Monoclinic TlInS 2x Se 2(1-x) Crystals

• Published in: International journal of infrared and millimeter waves Vol. 25; no. 5; pp. 735 - 747
• Main Authors: Samedov, S. R., Baykan, O., Gulubayov, A.
• Format: Journal Article
• Language: English
• Published: 01.05.2004
• ISSN: 0195-9271
• DOI: 10.1023/B:IJIM.0000027575.29370.78

Near IR properties of the mixed TlInS2xSe2(1-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(1-x) crystals, which are perspective materials for IR applications. From the temperature dependence's of conductivity in the direction perpendicular to c- axis the band gap E = 2.22 eV was determined for -TlInS2 crystals. The impurity centres were determined located at 0.4,0.73 eV and 0.3,0.48, 1.12 eV for the direction of current i//c and i c, respectively. The concentration of the centres located at 0.48 and 1.12 eV were calculated to be NA - ND = 4.8 * 10 cm and 1.9 * 10 cm, respectively. It was found that in the solid solutions TlInS2xSe2(1-x) for 0.3 x 1, the conductivity follows the dependence (v) = 0* 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(1-x) crystals make them perspective for practical applications: switching and memory effects, N-type current-voltage characteristics, induced conductivity etc.