Variable-range hopping conductivity in Cu2ZnGeSe4 single crystals

• Resistivity of single crystalline p-Cu2ZnGeSe4 is investigated between 10 and 300 K.
• Variable-range hopping conduction of the Mott type is established below ~230 K.
• Width and density of the localized states of the acceptor band are estimated.
• Localization radii and Bohr radius of the localized carriers are obtained.

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