Features of the band structure and conduction mechanisms of $n$-HfNiSn heavily doped with Y

The crystalline and electronic structures, energy, kinetic, and magnetic characteristics of $n$-HfNiSn semiconductor heavily doped with Y acceptor impurity are studied in the ranges: $T$ = 80–400 K, $N_{A}^{Y}\approx$ 1.9 $\times$ 10$^{20}$–5.7$^{21}$ cm$^{-3}$ ($x$ = 0.01–0.30), and $H\le$ 10 kG. The nature of the mechanism of structural defect generation is determined, which leads to a change in the band gap and the degree of semiconductor compensation, the essence of which is the simultaneous reduction and elimination of structural donor-type defects as a result of the displacement of $\sim$1% of Ni atoms from the Hf (4$a$) site, and the generation of structural acceptor-type defects by substituting Hf atoms with Y atoms at the 4$a$ site. The results of calculations of the electronic structure of Hf$_{1-x}$Y$_{x}$NiSn are in agreement with the experimental data. The discussion is performed within the Shklovskii–Efros model of a heavily doped and compensated semiconductor.