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Journal of Physical Studies 12(4), Article 4703 [6 pages] (2008)
DOI: https://doi.org/10.30970/jps.12.4703 OPTICAL AND PHOTOELECTRIC SPECTROSCOPY DEFECT OF PHOTOREFRACTIVE Sn$_2$P$_2$S$_6$ AND (Sn,Pb)$_2$P$_2$S$_6$ CRYSTALSR. V. Gamernyk{1}, Yu. P. Gnatenko{2}, A. G. Slivka{3}
{1}Ivan Franko National University of Lviv, 8, Kyryla i Mefodija St., UA--79005, Lviv,
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The low-temperature studies of absorption, photoluminescence, photodiffusion and photoconductivity spectra of еру Sn$_{2}$P$_{2}$S$_{6}$ and (Sn,Pb)$_{2}$P$_{2}$S$_{6}$ crystals were carried out in the wide spectral range 0.8-3.5 eV. These allow to determine the position of defect energy levels relatively to the crystal energy bands. It was shown that the photoionization transitions from the level with the energy $E_{v}+ 1.35$\,eV to the conduction band are caused by the appearance of the electronic metastable state. In the optical and photoelectric spectra several bands were revealed with the energy more than the band gap of the crystal ($E_g$=2.5\,eV). It was established that these bands are caused by the optical transitions between a valency band and some upper conduction bands. It was shown that the electron-hole recombination caused by the band-to-band transitions with the participation of the upper conduction subbands is fast and corresponds to the nanosecond region.
PACS number(s): 71.20.Nr, 71.55.Ht, 72.20.Jv, 78.20.Ci, 78.55.Hx