Electronic properties of Cu₂(Zn, Cd)SnS₄ determined by the high-field magnetotransport

Abstract

Resistivity, ρ (T), and magnetoresistance (MR) are investigated in the Cu2Zn1-xCdxSnS4 single crystals for compositions x ≡ Cd/(Zn + Cd) = 0.15 – 0.24, in the temperature range of T ~ 50 – 300 K in pulsed magnetic fields of B up to 20 T. The Mott variable-range hopping (VRH) conductivity is established within wide temperature intervals lying inside ΔT M ~ 60 – 190 K for different x. The deviations from the VRH conduction, observable above and below ΔT M, are connected to the nearest-neighbor hopping regime and to the activation on the mobility threshold of the acceptor band (AB) with width W ≈ 16 – 46 meV. The joint analysis of ρ (T) and positive MR permitted determination of other important electronic parameters. These include the localization radius, α ≈ 19 – 30 Å, the density of the localized states, g (μ) ≈ (1.6 – 21)×1017 meV–1 cm–3 at the Fermi level μ, and the acceptor concentration, N A ~ (6 – 8)×1019 cm–3, for various x and in conditions of different vicinity of the investigated samples to the metal-insulator transition. In addition, details of the AB structure, including positions of μ and of the mobility threshold, Ec , are found depending on the alloy composition.