Low-temperature photoluminescence in layered structured TlGa0.5In0.5Se2 crystals

Photoluminescence (PL) spectra of TlGa0.5In0.5Se2 layered crystals have been studied in the wavelength region of 900–1020 nm and in the temperature range of 10–61 K. A broad PL band centered at 951 nm (1.304 eV) was observed at T = 10 K. Variations of emission band has been studied as a function of excitation laser intensity in the 0.15–51.5 mW cm−2 range. The analysis of the spectra reveals that the peak energy position changes with laser excitation intensity (blue shift). This behavior of the emission band is in agreement with the idea of separation inhomogeneity of donor–acceptor pairs. Radiative transitions from donor level located at 647 meV below the bottom of conduction band to shallow acceptor level located at 22 meV above the top of the valence band were suggested to be responsible for the observed PL band.

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► Photoluminescence (PL) measurements were carried out in 10–61 K range.
► Variation of PL band was studied in 1.5–51.5 mW cm−2 laser excitation range.
► The peak energy position changes with laser excitation intensity (blue shift).
► Radiative transitions from donor to acceptor levels are responsible for PL band.