Low-temperature absorption edge and photoluminescence in layered structured Tl2Ga2S3Se single crystals

The emission band spectra of Tl2Ga2S3Se crystals have been studied in the temperature range 10-60 K and in the wavelength region 505-605 nm. A broad photoluminescence (PL) band centered at 550 nm (2.25 eV) was observed at T=10 K. Variation of emission band has been studied as a function of excitation laser intensity in the 0.3-41.5 mW cm−2 range. Radiative transitions from the shallow donor level Ed=0.01 eV to the moderately deep acceptor level Ea=0.16 eV were suggested to be responsible for the observed PL band.