Low-temperature visible photoluminescence spectra of TlGaSe2 layered crystal

Abstract

The photoluminescence (PL) spectra of TlGaSe layered single crystals were investigated in the 8.5}35 K temperature, 0.2}15.2 W cm\ excitation laser intensity, and in the 600}700 nm wavelength range. The PL spectrum has a slightly asymmetric Gaussian lineshape with a peak position located at 1.937 eV (640 nm) at 8.5 K. The PL is quenched with increasing temperature. The blue shift of the PL peak and the sublinear increase of the PL intensity with increasing laser intensity is explained using the inhomogenously spaced donor}acceptor pair recombination model. Analysis of the data indicates that the PL band is due to donor}acceptor recombination. A shallow acceptor level and a moderately deep donor level are, respectively, introduced at 0.012 eV above the top of the valence band and at 0.317 eV below the bottom of the conduction band. An energy-level diagram for radiative donor}acceptor pair recombination in TlGaSe layered single crystals is proposed

Excitation intensity and temperature‐dependent photoluminescence and optical absorption in Tl4Ga3InSe8 layered crystals

“…A high photosensitivity in the visible range of spectra, high birefringence in conjunction with a wide transparency range of 0.6-16 µm make this crystal useful for optoelectronic applications [7]. Previously we studied the photoluminescence (PL) of TlGaSe 2 crystals and observed a broad emission band centered at 640 nm, which was assigned to donor-acceptor pair recombination [8]. Moreover, recently we have studied PL spectra of Tl 4 In 3 GaSe 8 crystal in the 16-300 K temperature range and observed two broad emission bands centered at 589 and 633 nm, which we attributed to the transitions from two upper conduction bands to shallow acceptor levels [9].…”

Excitation intensity- and temperature-dependent photoluminescence in layered structured Tl2GaInSe2S2 crystals

“…Similar transitions involving such donor levels have also been revealed for other layered thallium chalcogenides. 13,14,16,27 IV. CONCLUSION TGISS crystals were characterized by x-ray powder diffraction and EDS analysis.…”

“…10 Earlier, we studied the low-temperature photoluminescence (PL) of ternary TlGaSe 2 and TlInS 2 crystals and observed one and two broad emission bands, respectively, which were assigned to donoracceptor pair (DAP) recombination. 13,14 Moreover, recently, we have investigated the low-temperature PL spectra of quaternary Tl 2 InGaSe 4 and Tl 2 InGaS 4 crystals and revealed one and three broad emission bands, respectively, which were attributed to the transitions from moderately deep donor to shallow acceptor levels. 15,16 In the present paper, we report the first results of the intensity variations of the PL spectra with temperature (17-62 K) and laser excitation intensity (0.1-55.7 mW cm À2 ) in TGISS crystals.…”

Investigation of structure and carrier recombination in TlGaSe2layered crystals

“…In TlGaSe 2 we may neglect surface related and radiative lifetimes because of the low diffusion to the surfaces [7] and negligible radiation probability [10], respectively. We also assume that trap-assisted Auger recombination is not important.…”