Low-temperature visible photoluminescence spectra of TlGaSe2 layered crystal

The photoluminescence (PL) spectra of TlGaSe2 layered single crystals were investigated in the 8.5-35 K temperature, 0.2-15.2 W cm(-2) excitation lase r intensity, and in the 600-700 nm wavelength range. The PL spectrum has a slightly asymmetric Gaussian lineshape with a peak position located at 1.93 7 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 w ith increasing laser intensity is explained using the inhomogenously spaced donor-acceptor pair recombination model. Analysis of the data indicates th at the PL band is due to donor-acceptor recombination. A shallow acceptor l evel and a moderately deep donor level are, respectively, introduced at 0.0 12 eV above the top of the valence band and ar 0.317 eV below the bottom of the conduction band. An energy-level diagram for radiative donor-acceptor pair recombination in TlGaSe2 layered single crystals is proposed (C) 2000 Elsevier Science B.V. All rights reserved.