Features of the acceptor band and properties of localized carriers from studies of the variable-range hopping conduction in single crystals of p-Cu2ZnSnS4

Resistivity, ρ(T), in single crystals of p-Cu2ZnSnS4 is investigated in the temperature interval of T∼300−10 K. Below ∼200 K, ρ(T) exhibits an activated character obeying between ∼130−150 K and ∼30−70 K the Mott variable-range hopping conduction law. Analysis of the experimental data yields typical values of the relative acceptor concentration, N/Nc∼0.72−0.84, where Nc ≈8×1018 cm−3 is the critical concentration of the metal–insulator transition (MIT), and those of a/aB∼3.5−6.4, where a is the localization radius and aB ≈13 Å is the Bohr radius, respectively. Width of the acceptor band, W∼11−22 meV, centered at the energy EB∼50−60 meV above the top of the valence band, is estimated implying a high degree of the microscopic lattice disorder in the investigated p-Cu2ZnSnS4 samples. Typical values of the density of the localized states, g∼(1−3)×1017 cm−3 meV−1, are estimated, as well.