Instability of DX-like impurity centers in PbTe:Ga at annealing

Abstract

The kinetics of variation in the resistance of PbTe:Ga single crystals, with their Fermi level pinned within the band gap, during annealing at temperatures of up to 400°C was studied for the first time. It is shown that annealing the crystals for only several minutes at 200–250°C leads to the transformation of the material, which is semi-insulating at low temperatures, into a strongly degenerate semiconductor with a free electron concentration of about 10−18 cm−3. In other words, annealing results in the decomposition of DX-like impurity centers, which account for Fermi level pinning within the PbTe:Ga band gap. The corresponding activation energy is determined. It is found that high-temperature annealing at about 400°C promotes the tendency to a partial recovery of semi-insulating properties.