Optical features of novel semiconducting crystals Tl1-xGa1-xSnxSe2 (x=0.05; 0.1)

The results of the novel Tl_1-xGa_1-xSn_xSe₂ single crystals (x = 0.05; 0.1) growth together with complex studies of their optical, electric and photoelectric properties are presented. Semiconductor crystalline alloys Tl₂Sе, Ga(In)₂Sе₃, SnSе₂ possessing congruent melting features has been served as components for the quasi-ternary systems. The Tl₂Se-Ga₂Se₃ was melted congruently at temperature 1073 K. Two compounds existied for the Tl₂Sе-In₂Sе₃system: TlInSe₂ melting congruently at 1023 K, and Tl₂Sе-In₂Sе₃ within congruent melting nature at 1029 K. Isothermal section of the Tl₂Se-Ga₂Se₃-SnSe₂ system at 520 K have been constructed from X-ray phase and formation of the ternary compounds Tl₄SnSе₄, Tl₂SnSе₃, TlGaSе₂ was confirmed. The spectral dependences of the absorption coefficients near the fundamental absorption have been studied with respect to direct as indirect dipole allowed inter-band transitions realized in the (TlGaSe₂)_1-x(SnSe₂)_x crystals for the studied temperature range. Follwing the Urbach's energy the role of electron-phonon interaction and structural disorder was analyzed.