High-field magnetotransport in Cu2ZnGeS4 single crystals

Abstract The quaternary chalcogenides, attracting much attention in recent time as promising solar energy materials, permit an effective optimization of their composition by the Ge incorporation. In particular, this implies an interest to the Cu 2 ZnGeS 4 compound, which utilization requires, however, a deeper understanding of its electronic properties in general. Here, we investigate magnetotransport of the p- type Cu 2 ZnGeS 4 single crystals, including resistivity, ρ ( T ), magnetoresistance (MR) and Hall effect, in pulsed magnetic fields up to B  = 20 T. The Mott variable-range hopping charge transfer has been established within a broad temperature interval of T between ∼100 and 200 K by investigations of ρ ( T ) in zero field. The positive and negative contributions to MR have been observed, attributing them to shrinkage of the impurity wave functions by the magnetic field and to the destructive interference of the hopping charge carriers, respectively. Observation of the negative Hall coefficient, R H ( T ), exhibiting the dependence close to that of ρ ( T ), gives a strong support to the Mott conduction mechanism in our p -type Cu 2 ZnGeS 4 material. In addition, the conductivity, connected with thermal activation of holes on the mobility edge, E c , has been identified both below and above the Mott conduction interval. Finally, the joint analysis of the ρ ( T ) and MR data has yielded a series of important microscopic parameters. These include such details of the hole spectrum in the acceptor band, as its semi-width, W , the density of localized states, g (μ), at the Fermi level, μ, the positions of μ and E c , as well as values of the localization radius of holes, a , and of the acceptor concentration, N A .