Analysis of the Hall effect in TlGaTe2 single crystals

The electrical resistivity and Hall coefficient of p-type TlGaTe2 crystals were measured in the temperature range of 110-320 K. The electrical resistivity, charge carrier density and Hall mobility data for the crystals have been analyzed by means of existing theories and models to determine the extrinsic energy levels, the carrier effective mass, the donor and acceptor concentrations and the dominant scattering mechanism in the crystal as well. The analysis of the temperature-dependent electrical resistivity recorded parallel and perpendicular to the crystal's axis (c-axis) reflected the existence of energy levels located at 0.26 and at 0.20 eV, respectively. The difference of these two energy levels is due to crystal anisotropy. The energy level at 0.26 eV was found to represent an acceptor level, as confirmed from Hall data analysis. The temperature dependence of the carrier density was analyzed by using the single-donor-single-acceptor model. The latter analysis revealed the carrier effective mass and the acceptor and donor concentrations as 0.73m0,4.10 x 1017 cm-3 and 1.20 x 1017 cm-3, respectively. The Hall mobility of TlGaTe2 is found to be limited by the scattering of hole-acoustic phonon interactions. The calculated theoretical mobility fits to the experimental one under the condition that the acoustic deformation potential is 11.0 eV, which is the energy position of the top of valence band maximum that is formed by the Te 5s states.