Features of conductivity mechanisms in heavily doped compensated V$_{1-x}$Ti$_{x}$FeSb semiconductor

The crystal and electronic structure and also the energy and kinetic properties of $n$-VFeSb semiconductor heavily doped with the Ti acceptor impurity are investigated in the temperature and Ti concentration ranges of $T$ = 4.2–400 K and $N^{\mathrm{Ti}}_{A}\approx$ 9.5 $\times$ 10$^{19}$–3.6 $\times$ 10$^{21}$ cm$^{-3}$ ($x$ = 0.005–0.20), respectively. The complex mechanism of the generation of acceptor and donor structural defects is established. It is demonstrated that the presence of vacancies at Sb atomic sites in $n$-VFeSb gives rise to donor structural defects (“a priori doping”). Substitution of the Ti dopant for V in VFeSb leads simultaneously to the generation of acceptortype structural defects, a decrease in the number of donor defects, and their removal in the concentration range of 0 $\le x\le$ 0.03 via the occupation of vacancies by Sb atoms, and the generation of donor defects due to the occurrence of vacancies and an increase in their number. The result obtained underlies the technique for fabricating new $n$-VFeSb-based thermoelectric materials. The results are discussed in the context of the Shklovsky–Efros model for a heavily doped compensated semiconductor.