Photoluminescence (PL) spectra of GaS_0.75Se_0.25 layered single crystals have been studied in the wavelength region of 500-850 nm and in the temperature range of 10-200 K. Two PL bands centered at 527 (2.353 eV, A-band) and 658 nm (1.884 eV, B-band) were observed at T = 10 K. Variations of both bands have been studied as a function of excitation laser intensity in the range from 8x10^-3 to 10.7 W cm^-2. These bands are attributed to recombination of charge carriers through donor-acceptor pairs located in the band gap. Radiative transitions from shallow donor levels located 0.043 and 0.064 eV below the bottom of conduction band to acceptor levels located 0.088 and 0.536 eV above the top of the valence band are suggested to be responsible for the observed A- and B-bands in the PL spectra, respectively.

Keywords: photoluminescence, semiconductor compounds, layered crystals, GaS0.75Se0.25

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