Dynamics of polarized magnetoluminescence of localized excitons in mixed GaSe–GaTe crystals

Polarization of radiation of triplet localized excitons induced by an external magnetic field in uniaxial GaSe–GaTe solid solutions (Voigt geometry) has been investigated using the time-resolved spectroscopy method. The linear radiation polarization occurring in a magnetic field is caused by a different behavior of radiation components polarized with $\mathbf{E}\parallel\mathbf{B}$ and $\mathbf{E}\perp\mathbf{B}$ ($\pi$- and $\sigma$-components, respectively). Under steadystate conditions of excitation by unpolarized light, the $\pi$-component intensity increases in the field, whereas the $\sigma$-component intensity gradually decreases with increasing field. It has been shown that the dependences of the $\pi$- and $\sigma$-component intensities $I_{\pi}(B,t)$ and $I_{\sigma}(B,t)$ on the magnetic field significantly change for the lifetime $t$ of excited states. The different decay rates of $\pi$- and $\sigma$-components lead to the strong time dependence of the linear polarization of exciton radiation induced by a magnetic field. The degree of linear radiation polarization at the exciton luminescence band maximum in fields $B\ge$ 0.4 T at long times $t$ approaches unity. A theoretical description of the observed dependences $I_{\pi}(B,t)$ and $I_{\sigma}(B,t)$ has been proposed. The fine structure parameters and lifetimes of triplet excitons in different spin states have been determined by comparing the theory and experiment.