Turkish Journal of Physics




$p-TlGaSe_2$, $p-TlIn_{0.3}Ga_{0.7}Se_2$ and $p-TlIn_{0.5}Ga_{0.5}Se_2$ single crystals were grown by the modified Bridgman-Stockbarger method in our crystal growth laboratory. The absorption measurements were carried out on $p-TlIn_xGa_{(1-x)}Se_2$ samples in temperature range 10-300 K in steps of 10 K. The binding energies of $p-TlGaSe_2$, $p-TlIn_{0.3}Ga_{0.7}Se_2$ and $p-TlIn_{0.5} Ga_{0.5}$ $Se_2$ were obtained as \\ 35.0 meV, 16.5 meV and 14.5 meV, respectively. THe direct band gaps were calculated as 2.244 eV, 2.195 eV, 2.164 eV in $p-TlGaSe_2$, 2.158 eV, 2.131 eV, 2.098 eV in $p-TlIn_{0.3}Ga_{0.7}Se_2$, and 2.107 eV, 2.075 eV, 2.019 eV in $p-TlIn_{0.5}Ga_{0.5}Se_2$ respectively, at sample temperatures of 10 K, 140 K and 300 K. The indirect band gaps were calculated as 2.196 eV, 2.127 eV, 2.073 eV in $p-TlGaSe_2$ 2.130 eV, 2.101 eV, 2.064 eV in $p-TlIn_{0.3}Ga_{0.7}Se_2$ and 2.090 eV, 2.054 eV, 2.004 eV in $p-TlIn_{0.5}Ga_{0.5}Se_2$ respectively, at 10 K, 140 K and 300 K. There is an abrupt change in the energy peak for $p-TlGaSe_2$ in the temperature range 135-150 K. The values that we obtained from the energy peak change may be at a phase transition temperature.

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