INFLUENCE OF ZN DOPING ON OPTICAL PROPERTIES OF TLGASE2 CHALCOGENIDE SINGLE CRYSTALS
DOI:
https://doi.org/10.32782/pet-2021-1-4Keywords:
layered semiconductors, solid solutions, optical absorption, band gap, Urbach energy, defect levelsAbstract
The absorption spectra of TlGaSe2: Zn (5mol%ZnSe) single crystals in the temperature region 100-300 К have been studied. The doping changes the shape of the absorption curves and increases the blur of the edge of the absorption band. Urbach's energy increases from 59 meV for unalloyed to 68 meV for doped crystals at room temperature. Obviously, doping creates structural defects that increase the random modulation of the electric field in the crystal, which leads to the blurring of the absorption edge. The direct and indirect band gaps of TlGaSe2: Zn solid solutions are less than for pure crystals, and at room temperatures are found to be 2.08 eV and 1.92 eV, respectively.Doping causes the essential increase in the absorption coefficient at 100 K in the energy range from 2.17 eV to 2.21 eV. Probably, in this area lie the energy levels of defects, associated with Zn atoms. The abrupt change in the absorption coefficient may also indicatethe approach to the temperature of phase transition from the commensurate ferroelectric to the incommensurate phase, since in pure and doped crystals these temperatures, as a rule, do not coincide.
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