Variable-range hopping conductivity in Cu2ZnGeSe4 single crystals

Abstract

Resistivity, ρ(T), of the Cu2ZnGeSe4 single crystals is investigated between T~10 and 300K. The Mott variable-range hopping (VRH) conductivity is observed in the temperature interval of ~80–230K. Analysis of the Mott VRH conductivity yields the values of the semi-width of the acceptor band, W≈13–15meV, the relative acceptor concentration, NA/Nc≈0.86–0.89, at the critical concentration of the metal–insulator transition, Nc≈6.3×1018cm−3, the values of the localization radius, a/aB≈7–9 with the Bohr radius aB≈13.5Å, the mean acceptor energy E0≈82meV and the mean density of the localized states, g≈(1.7–2.1)×1017meV−1cm−3.