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

The kinetics of variation in the resistance of PbTe:Ga single crystals, wit h their Fermi level pinned within the band gap, during annealing at tempera tures of up to 400 degrees C was studied for the first time. It is shown th at annealing the crystals for only several minutes at 200-250 degrees C lea ds to the transformation of the material, which is semi-insulating at low t emperatures, 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 lev el pinning within the PbTe:Ga band gap. The corresponding activation energy is determined. It is found that high-temperature annealing at about 400 de grees C promotes the tendency to a partial recovery of semi-insulating prop erties. (C) 2000 MAIK "Nauka/Interperiodica".