TEMPERATURE-DEPENDENCE OF FREE-EXCITON PHOTOLUMINESCENCE IN CRYSTALLINE GATE

We present a photoluminescence study of the free-exciton singlet and t riplet ground states in GaTe as a function of temperature from 5 to 40 K. Over the range 5-25 K, the temperature variation of excitonic-emis sion linewidth and peak energy comes mainly from exciton-acoustic-phon on interactions via the deformation potential. The contribution from e xciton scattering by optical phonons of energy 14 meV begins at temper atures above approximately 25 K. The exciton-optical-phonon interactio n is the dominant scattering process above 30 K and effectively dissoc iates excitons since the energy of the optical phonon mode is close to the exciton binding energy, The luminescence thus decreases rapidly a bove 30 K and disappears at about 40 K.