Temperature- and excitation intensity-dependent photoluminescence in Ga4Se3S layered crystals

Photoluminescence (PL) spectra of Ga4Se3S layered single crystals have been studied in the wavelength region of 535–855 nm and in the temperature range of 16–200 K. Two PL bands centered at 572 nm (2.168 eV, A-band) and 652 nm (1.902 eV, B-band) were observed at T = 16 K. Variations of both bands have been studied as a function of excitation laser intensity in the range 0.10–149.92 mW cm−2. The A-band is attributed to radiative transition from donor level located 0.125 eV below the bottom of conduction band to shallow acceptor level located 0.011 eV above the top of the valence band. The increase of the width of B-band and its quenching with increasing temperature is explained using the configurational coordinate model.