ИСТИНА

In order to reveal iron-induced deep level in the energy spectrum of PbTe and construct the models of the electronic structure rearrangement with increasing of impurity concentration and under pressure we investigate galvanomagnetic properties (T=4.2-300 K, B<0.07 T) of Pb1-yFeyTe alloys at atmospheric pressure and under hydrostatic compression up to 10 kbar. It is found that with the increase of iron content in PbTe free hole concentration decreases and reaches saturation value p=(7-8)∙1017 cm-3 in the interval of impurity content y=0.005-0.012. Further doping leads to the p-n inversion of the conductivity type and monotonous increase of electron concentration in heavily doped alloys. Under pressure Hall coefficient at helium temperatures decreases monotonously by approximately four times indicating an increase in the hole concentration due to the pinning of Fermi level by the impurity level and redistribution of electrons between valence band and impurity states. Obtained experimental results are explained in the frame of the model assuming the formation of resonant iron impurity level, which stabilizes the Fermi level under the valence band top in the finite interval of iron content. Under pressure the gap decreases linearly with the rate approximately -7.4 meV/kbar while the iron level only slowly moves relative to the middle of the gap. Thus an increase of pressure results in shifting of the valence band top from the iron resonant level, flowing of electrons from the valence band to the level and increasing in the free hole concentration. Using the pressure dependence of the Hall coefficient in the frame of six-band Dimmocks’s dispersion relation we calculated pressure dependencies of Fermi level and free hole concentration varying the energy position of iron level and pressure coefficient of its movement relative to the middle of the gap.