Transport properties of TlIn1-xGaxSe2 (0≤x≤0.3) crystals

Single crystals of TlIn1-x Ga (x) Se-2 solid solutions have been grown by the Bridgman-Stockbarger method. As shown by x-ray diffraction, the solid solutions crystallize in tetragonal symmetry, and their lattice parameters decrease with decreasing average atomic weight. The electrical conductivity and Hall coefficient of the solid solutions have been measured as functions of temperature, and their principal semiconductor parameters have been determined. Pseudopotential band-structure calculations have been used to analyze the origins of the valence and conduction bands in the parent compound TlInSe2. The results indicate that the increase in the band gap of the TlIn1-x Ga (x) Se-2 solid solutions upon partial gallium substitution for indium in TlInSe2 is due to the shift of its valence band to lower energies.