Defect characterization of cTl(4)GaIn(3)Se(2)S(6) layered single crystals by photoluminescence

Photoluminescence (PL) spectra of Tl4GaIn3Se2S6 layered crystals grown by the Bridgman method have been studied in the energy region of 2.02-2.35 eV and in the temperature range of 16-45 K. A broad PL band centered at 2.20 eV was observed at T = 16 K. Variations of emission band has been studied as a function of excitation laser intensity in the 0.1 to 149.9 mW cm(-2) range. Radiative transitions from shallow donor level located at 10 meV below the bottom of conduction band to moderately deep acceptor level located at 180 meV above the top of the valence band were suggested to be responsible for the observed PL band. An energy level diagram showing transitions in the band gap of the crystal was plotted taking into account the results of present work and previously reported paper on thermally stimulated current measurements carried out below room temperature. Analysis of the transmission and reflection measurements performed in the wavelength range of 400-1030 nm at room temperature revealed the presence of indirect transitions with 2.22 eV band gap energy.