Below and above bandgap excited photoluminescence inTl4InGa3S8 layered single crystals

Abstract

Photoluminescence (PL) spectra ofTl4InGa3S8 layered single crystals grown by the Bridgman method have been studied in the550–710 nm wavelength and 80–300 K temperature ranges with below bandgap excitation(λexc = 532 nm),and in the 420–600 nm wavelength and 30–300 K temperature ranges with above bandgap excitation(λexc = 325 nm). The broad emission bands centered at 580 nm (2.14 eV) and 496 nm (2.49 eV) were observed atT = 80 and 30 K for below and above bandgap excitation processes, respectively. Variations inemission spectra have been studied as a function of excitation laser intensity in the10.3–429.7 mW cm−2 range for below bandgap excitation. Radiative transitions from the donor levels located at0.02 and 0.37 eV below the bottom of the conduction band to the deep acceptor levellocated at 0.20 eV above the top of the valence band were proposed to be responsible forthe observed PL bands. From x-ray powder diffraction and EDS analysis, themonoclinic unit cell parameters and compositional parameters, respectively, weredetermined.