The absortion properties of p-type $TlIn_xGa_{1-x}Se_2$ and $TlGaSe_2$

Özet

p — $TlGaSe_2$, p — $TlIn_{o.3}Ga_{o.7}Se_2$ and p — $TlIn_{o.5}Ga_{o.5}Se_2$ 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 — $TlIn_{o.3}Ga_{o.7}Se_2$ and p — $TlIn_{o.5}Ga_{0.5}Se_2$ 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 - $TlIn_{o.3}Ga_{o.7}Se_2$, and 2.107 eV, 2.075 eV, 2.019 eV in p - $TlIn_{o.5}Ga_{o.5}Se_2$ 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 - $TlIn_{o.3}Ga_{o.7}Se_2$ and 2.090 eV, 2.054 eV, 2.004 eV in p — $TlIn_{o.5}Ga_{0.5}Se_2$ 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.