Vanadium deep impurity level in diluted magnetic semiconductors Pb$_{1-x-y}$Sn$_x$V$_y$Te

The crystal structure, Sn and V distribution over the length of single-crystal ingots, and galvanomagnetic effects in low magnetic fields (4.2 K $\le T\le$ 300 K, $\mathbf{B}\le$ 0.07 T) in Pb$_{1-x-y}$Sn$_x$V$_y$Te alloys ($x$ = 0.05–0.21, $y\le$ 0.015) are studied. It is shown that all the samples are single-phase, while the Sn and V concentrations exponentially increase from the beginning to the end of the ingots. Upon doping with V, a decrease in the concentration of free holes and a metal-insulator transition are found. They are related to the appearance of a deep impurity level of V in the band gap, electron redistribution between the level and the valence band, and pinning of the Fermi-level to the impurity level. The shift rate of the V level relative to the conduction band bottom is determined and a diagram of the reconstruction of the electronic structure of the Pb$_{1-x-y}$Sn$_x$V$_y$Te alloy upon varying the host composition is suggested.