Temperature and pressure coefficients of iron resonant impurity level in PbTe

Abstract

We investigate temperature dependences of galvanomagnetic parameters in weak magnetic fields (4.2 ≤ T ≤ 300 K, B ≤ 0.07 T) in the p-Pb1−yFeyTe alloy from the middle part of the single-crystal ingot, where the Fermi level is pinned by the resonant impurity level lying under the top of the valence band. Experiments are performed under hydrostatic compression up to 10 kbar. Using scanning electron microscopy, we find microscopic inclusions of the secondary phase enriched with iron and show that the main phase is characterized by a good uniformity of the spatial distribution of impurities. A monotonous increase of the free hole concentration at liquid-helium temperature under pressure and anomalous temperature dependences of the Hall coefficient in the whole investigated pressure range are revealed. Experimental results are explained by a model assuming pinning of the Fermi level by the impurity level and a redistribution of electrons between the valence band and impurity states with increasing temperature and under pressure. In the framework of the two-band Kane dispersion law, theoretical temperature dependences of the Hall coefficient under pressure, which are in satisfactory agreement with the experimental ones at low temperatures, are calculated and temperature and pressure coefficients of the iron deep level are determined. Diagrams of the electronic structure rearrangement with increasing temperature for Pb1−yFeyTe at pressures up to 10 kbar are proposed.