Optical absorption related to Fe impurities in TlGaSe₂

Abstract

Absorption measurements of TlGaSe2 crystals intentionally doped with Fe show growing optical transitions below the band gap energies as impurity concentration increase. The comprehensive theoretical analysis is performed for elucidation of subband absorption spectra by using valence band‐to‐Fe centre optical transitions. We identify three deep donor levels at 1.33, 1.475, and 1.77 eV, respectively, with rather similar doping and temperature dependences. Energy position of levels follows temperature shrinkage of the lowest direct band gap rather than of the indirect band gap. Electron–phonon and static structural broadening is evaluated and the corresponding configurational coordinate diagram of Fe centres is constructed. Subtraction of calculated band‐to‐Fe centre absorption from the total absorption spectrum shows that the fundamental absorption edge structure of the TlGaSe2 crystal remains almost unchanged at least to the doping level of Fe = 0.5%. However, Fe impurities cancel low‐temperature photoluminescence.

Band edge photoluminescence of undoped and doped TlInS 2 layered crystals

“…A small tail is observed down to 1.7 eV for the B doping, and a strong one, down to 1.35 eV, for Ag doping. The last is similar to bands observed for the isostructural semiconductors after Fe doping in TlGaS 2 [16] and in TlGaSe 2 [17]. However, we have found that the Er incorporation does not show an evidence for sub-gap absorption.…”

Novel Quaternary TlGaSn2Se6 Single Crystal as Promising Material for Laser Operated Infrared Nonlinear Optical Modulators

“…Moreover, the huge anharmonic phonon contribution that is typical for chalcogenide crystals may also be superimposed. Similar absorption spectra were obtained in [53] for TlGaSe 2 with Fe admixtures. The authors suggest that these absorption bands are associated with the substitution of the "host" metal atoms by Fe atoms.…”

Study of optical absorption in TlGaSe2:Zn2+ single crystals

“…Apart from the direct and indirect transmission bands and the temperature points of phase transitions, the previous investigations on the subject have also been concerned with the phonon energy, the temperature coefficient and the so-called 'steepness' parameter of the Urbach energy, as well as the Debye parameter of A III B III C 2 VI single crystals [4,[16][17][18][19].…”