Electrophysical Characteristics of TlBr Crystals Grown in Various Ambients

Electrophysical characteristics were measured for TlBr crystals grown by Bridgman technique in various ambients: vacuum, Ar, air, Br. The dark resistivity of the crystals measured by Van der Pauw method was (1.0-2.3) times 10¹⁰ Ohmmiddotcm at 18 degC. The growth ambient had a profound influence on optical, MCL and deep traps spectra of TlBr, but not on the position of the Fermi level pinned around 0.80-0.85 eV from the valence band edge. The major traps had activation energies of 0.60, 0.50, 0.36, 0.27 and 0.19 eV. Crystals grown in vacuum showed the highest concentration of deep traps while the lowest density of traps was detected in the ingots grown in air. The concentration of deep traps was found to decrease dramatically upon addition of a small amount of Br into the ampoule with constituent components. However, when the amount of Br was increased, the direction of the crystal parameters changes was ambiguous. We assume that this is due to the formation of the second phase of TlBr₃. MCL spectra measured at 95 K showed the presence of 2.98 and 2.70 eV exciton lines and of wide defect bands at 2.46 eV, 2.25 eV and 1.90 eV.