Comparative study of low-temperature photoluminescence and thermally stimulated current in quinary Tl4Ga3InSe6S2 layered crystals

Photoluminescence (PL) and thermally stimulated current (TSC) spectra of Tl4Ga3InSe6S2 layered crystals grown by Bridgman method have been studied in the wavelength region of 560-690 nm and the temperature range of 15-45 K (PL) and in the temperature region of 10-90 K (TSC). A broad PL band centered at 620 nm (2.00 eV) was observed at T=15 K. Variations of emission band has been studied as a function of excitation laser intensity in the 0.7-36.5 mW cm−2 range. Radiative transitions from donor level located at 150 meV below the bottom of conduction band to shallow acceptor level located at 10 meV above the top of the valence band were suggested to be responsible for the observed PL band. TSC curve of Tl4Ga3InSe6S2 crystal exhibited one broad peak at about 41 K. The activation energy of trap level was found to be 11 meV. An energy level diagram showing transitions in the band gap of the crystal was plotted taking into account the results of PL and TSC measurements carried out below room temperature.