Deep and resonance states in A^IV B^VI semiconductors

Indium Substitution Effect on the Topological Crystalline Insulator Family (Pb1−xSnx)1−yInyTe: Topological and Superconducting Properties

“…This relaxation phenomenon can last for days until the resistivity reaches a stable value. Previous studies on Pb 1−x Sn x Te doped with group-III elements revealed similar time-dependent behavior, and it was explained in terms of the interaction between the crystal lattice and the non-equilibrium electron densities associated with the pinned chemical potential at the impurity level [52].…”

“…The topologically distinct band structure of SnTe (nontrivial, x = 1) and PbTe (trivial, x = 0) involves a change in the ordering of the conduction and valence bands at L points. This implies that the band gap of the alloy Pb 1−x Sn x Te first closes and then re-opens as x increases, as shown in Figure 5 [51][52][53]. It follows that there must be a topological quantum phase transition upon varying the Pb/Sn ratio in Pb 1−x Sn x Te, and experiments indicate that it occurs near x c ≈ 0.35 at low temperature [15,[52][53][54][55][56].…”

“…In this scenario, the large bulk resistivity in series with x = 0.25-0.35 is a consequence of indium sites introducing localized impurity states that pin the chemical potential [51,52]; the electronic properties then depend on the position and width of the indium level. In the region of compositions where the localized impurity band lies in the band gap or a position that is very close to the band edge, the free carrier concentration is extremely low at low temperature, which is reflected in the very large bulk resistivities for x ∼ 0.30 that we observe in the transport measurements.…”

Nonstoichiometry and Properties of SnTe Semiconductor Phase of Variable Composition

“…On the other hand, none of the models takes into account high concentration of NSD, although it must significantly affect the electronic spectrum. In (Nimtz G., Schlicht, 1985;Heinrich, 1979;Kaydanov & Ravich, 1985;Sobolev, 1981) no impurity levels or bands in the SnTe energy gap were detected. According to the theoretical estimations (Kaydanov & Ravich, 1985), the defect potential in narrow-gap semiconductors like SnTe must be short-range due to interband screening, significant for a small energy gap, and a large value of static dielectric constant connected with the presence of soft modes.…”

“…In (Nimtz G., Schlicht, 1985;Heinrich, 1979;Kaydanov & Ravich, 1985;Sobolev, 1981) no impurity levels or bands in the SnTe energy gap were detected. According to the theoretical estimations (Kaydanov & Ravich, 1985), the defect potential in narrow-gap semiconductors like SnTe must be short-range due to interband screening, significant for a small energy gap, and a large value of static dielectric constant connected with the presence of soft modes. Highly localized potential must result in the formation of deep levels, the impurity state energy can fall within a zone of allowed energies creating a resonant (quasi-local) state.…”