Electrical properties of Pb$_{1-x}$Mn$_x$Te single crystals with an excess of tellurium

The effect of excess Te atoms (as high as 0.5 at%) and thermal treatment at 473 K for 120 h on the electrical conductivity $\sigma$, the thermopower coefficient $\alpha$, and the Hall coefficient $R$ of Pb$_{0.96}$Mn$_{0.04}$Te single crystals in the temperature range $\sim$ 77–300 K is investigated. It is shown that excess atoms of tellurium predominantly act as acceptor impurity centers at low concentrations in unannealed samples and form antisite defects at relatively high concentrations (0.05 at% or higher) being located mainly in vacancies of the lead sublattice, and decrease the hole concentration. As a result of annealing, certain lattice defects (for example, deformational) are healed, and the accommodation process for Te atoms at lead-sublattice vacancies is intensified. These processes substantially affect the values of the electrical parameters, their temperature dependences, as well as the sign of the thermopower and Hall coefficients of the samples.