Study of trapping and recombination centres in Tl₂InGaTe₄ chain crystals by dark electrical conductivity and photoconductivity measurements

Abstract

Dark electrical conductivity and photoconductivity of Tl₂InGaTe₄ single crystals have been measured and analyzed in the temperature region 100–300 K. The dark electrical conductivity measurements revealed an intrinsic- or extrinsic-type of conductivity above or below 210 K, respectively. From intrinsic conductivity data analysis, the energy band gap of Tl₂InGaTe₄ crystals was determined as 0.85 eV. In the extrinsic region, the dark conductivity arises from a donor energy level located at 0.30 eV below the conduction band. The photocurrent increases with increasing illumination intensity. The recombination mechanism in the crystal changes as temperature decreases due to the effect of exponential trapping centres. Two trapping and/or recombination centres located at 89 and 27 meV were determined from the temperature dependence of the photocurrent, which decreased or increased with increasing temperature in the regions above or below 180 K, respectively.