Browsing by Author "Goksen, K."

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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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    Donor-acceptor pair recombination in gallium sulfide
    (American Institute of Physics, 2000-12-15) Aydınlı, Atilla; Gasanly, N. M.; Goksen, K.
    Low temperature photoluminescence of GaS single crystals shows three broad emission bands below 2.4 eV. Temperature and excitation light intensity dependencies of these bands reveal that all of them originate from close donor-acceptor pair recombination processes. Temperature dependence of the peak energies of two of these bands in the visible range follow, as expected, the band gap energy shift of GaS. However, the temperature dependence of the peak energy of the third band in the near infrared shows complex behavior by blueshifting at low temperatures followed by a redshift at intermediate temperatures and a second blueshift close to room temperature, which could only be explained via a configuration coordinate model. A simple model calculation indicates that the recombination centers are most likely located at the nearest neighbor lattice or interstitial sites. (C) 2000 American Institute of Physics. [S0021- 8979(00)04724-1].