Browsing by Subject "Defect levels"

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    Donor - acceptor pair recombination in Tl2InGaS4 layered crystals
    (2005) Goksen, K.; Gasanly, N.M.; Ozkan H.; Aydınlı, Atilla
    Photoluminescence (PL) spectra of Tl2InGaS4 layered single crystals were studied in the temperature range 15-150 K and wide laser excitation intensity range 0.01-110.34 Wcm-2. We observed a total of three PL bands, one centered at 542 nm (2.286 eV, A-band), one at 607 nm (2.041 eV, B-band), and one at 707 nm (1.754 eV, C-band), at various excitation intensities. The A- and the B-bands were determined to be due to radiative transitions from moderately deep donor levels located at 0.189 and 0.443 eV below the bottom of the conduction band to the shallow acceptor levels at 0.025 and 0.016 eV above the top of the valence band, respectively. The blue shift of the C-band peak energy and the quenching of the PL with increasing temperature are explained within the configuration coordinate model. The observation in the PL spectra of different emission bands in the sequence of B-, C- and A-bands at low, moderate, and high excitation laser intensities, respectively, are attributed to the shift of the quasi-Fermi level with increasing excitation intensity.
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    Infrared photoluminescence from TlGaS2 layered single crystals
    (Wiley - V C H Verlag GmbH & Co., 2004) Yuksek, N. S.; Gasanly, N. M.; Aydınlı, Atilla; Ozkan, H.; Acikgoz, M.
    Photolimuniscence (PL) spectra of TlGaS2 layered crystals were studied in the wavelength region 500-1400 nm and in the temperature range 15-115 K. We observed three broad bands centered at 568 nm (A-band), 718 nm (B-band) and 1102 nm (C-band) in the PL spectrum. The observed bands have half-widths of 0.221, 0.258 and 0.067 eV for A-, B-, and C-bands, respectively. The increase of the emission band half-width, the blue shift of the emission band peak energy and the quenching of the PL with increasing temperature are explained using the configuration coordinate model. We have also studied the variations of emission band intensity versus excitation laser intensity in the range from 0.4 to 19.5 W cm-2. The proposed energy-level diagram allows us to interpret the recombination processes in TlGaS2 crystals.
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    Trap levels in layered semiconductor Ga2SeS
    (Elsevier, 2004) Aydınlı, Atilla; Gasanly, N. M.; Aytekin, S.
    Trap levels in nominally undoped Ga2SeS layered crystals have been characterized by thermally stimulated current (TSC) measurements. During the measurements, current was allowed to flow along the c-axis of the crystals in the temperature range of 10-300 K. Two distinct TSC peaks were observed in the spectra, deconvolution of which yielded three peaks. The results are analyzed by curve fitting, peak shape and initial rise methods. They all seem to be in good agreement with each other. The activation energies of three trapping centers in Ga2SeS are found to be 72, 100 and 150 meV. The capture cross section of these traps are 6.7×10-23, 1.8×10-23 and 2.8×10-22cm2 with concentrations of 1.3×1012, 5.4×1012 and 4.2×1012cm-3, respectively.