Abstract:Resistivity, ρ(T, x), of Cu2Zn(Sn x Ge1-x )Se4 (CZTGeSe) single crystals with x = 0-1, investigated at temperatures between T ~ 10-320 K, exhibits an activated character within the whole temperature range, attaining a minimum at x = 0.47. Magnetoresistance (MR) of CZTGeSe with x = 0.26, 0.47 and 0.64 is positive (pMR) in all measured fields of B up to 20 T at any T between ~40-320 K, whereas MR of samples with x = 0 and 1 contains a negative contribution (nMR). The dependence of ρ(T) at B = 0 gives e… Show more
“…As has been demonstrated recently 24,32 , the most probable mechanism of nMR in CZGS is connected with quantum interference effects in the Mott VRH conduction interval 46–50 . Therefore, we can utilize this mechanism for interpretation of nMR in our CZTGS alloys, too, especially taking into account the close similarity of the MR behavior in both materials, mentioned in Section “Experimental results”.…”
Section: Resultsmentioning
confidence: 57%
“…Generally, such features of nMR are quite uncommon for conventional doped semiconductors. However, they have been already observed in the pure CZGS 24 and, partially, in the Cu 2 ZnSn x Ge 1−x Se 4 alloys 32 .Figure 2The dependences of Δρ/ρ on B for x = 0 ( a ), 0.13 ( b ), 0.51 ( c ) and x = 0.70 ( d ).…”
Section: Resultsmentioning
confidence: 90%
“…In kesterites and related compounds, different mechanisms of the charge transfer have been observed within different temperature intervals Δ T 22–25,32–41 . These include (i) the nearest-neighbor hopping (NNH) at T lying within Δ T n , (ii) the Mott VRH hopping inside the interval Δ T M and (iii) thermal activation of charge carriers into an interval of delocalized states in the acceptor band at temperatures within Δ T a 42–44 .…”
Resistivity, ρ(T), and magnetoresistance (MR) are investigated in the Cu2ZnSnxGe1−xS4 single crystals, obtained by the chemical vapor transport method, between x = 0–0.70, in the temperature range of T ~ 50–300 K in pulsed magnetic field of B up to 20 T. The Mott variable-range hopping (VRH) conductivity is observed within broad temperature intervals, lying inside that of T ~ 80–180 K for different x. The nearest-neighbor hopping conductivity and the charge transfer, connected to activation of holes into the delocalized states of the acceptor band, are identified above and below the Mott VRH conduction domain, respectively. The microscopic electronic parameters, including width of the acceptor band, the localization radius and the density of the localized states at the Fermi level, as well as the acceptor concentration and the critical concentration of the metal-insulator transition, are obtained with the analysis of the ρ(T) and MR data. All the parameters above exhibit extremums near x = 0.13, which are attributable mainly to the transition from the stannite crystal structure at x = 0 to the kesterite-like structure near x = 0.13. The detailed analysis of the activation energy in the low-temperature interval permitted estimations of contributions from different crystal phases of the border compounds into the alloy structure at different compositions.
“…As has been demonstrated recently 24,32 , the most probable mechanism of nMR in CZGS is connected with quantum interference effects in the Mott VRH conduction interval 46–50 . Therefore, we can utilize this mechanism for interpretation of nMR in our CZTGS alloys, too, especially taking into account the close similarity of the MR behavior in both materials, mentioned in Section “Experimental results”.…”
Section: Resultsmentioning
confidence: 57%
“…Generally, such features of nMR are quite uncommon for conventional doped semiconductors. However, they have been already observed in the pure CZGS 24 and, partially, in the Cu 2 ZnSn x Ge 1−x Se 4 alloys 32 .Figure 2The dependences of Δρ/ρ on B for x = 0 ( a ), 0.13 ( b ), 0.51 ( c ) and x = 0.70 ( d ).…”
Section: Resultsmentioning
confidence: 90%
“…In kesterites and related compounds, different mechanisms of the charge transfer have been observed within different temperature intervals Δ T 22–25,32–41 . These include (i) the nearest-neighbor hopping (NNH) at T lying within Δ T n , (ii) the Mott VRH hopping inside the interval Δ T M and (iii) thermal activation of charge carriers into an interval of delocalized states in the acceptor band at temperatures within Δ T a 42–44 .…”
Resistivity, ρ(T), and magnetoresistance (MR) are investigated in the Cu2ZnSnxGe1−xS4 single crystals, obtained by the chemical vapor transport method, between x = 0–0.70, in the temperature range of T ~ 50–300 K in pulsed magnetic field of B up to 20 T. The Mott variable-range hopping (VRH) conductivity is observed within broad temperature intervals, lying inside that of T ~ 80–180 K for different x. The nearest-neighbor hopping conductivity and the charge transfer, connected to activation of holes into the delocalized states of the acceptor band, are identified above and below the Mott VRH conduction domain, respectively. The microscopic electronic parameters, including width of the acceptor band, the localization radius and the density of the localized states at the Fermi level, as well as the acceptor concentration and the critical concentration of the metal-insulator transition, are obtained with the analysis of the ρ(T) and MR data. All the parameters above exhibit extremums near x = 0.13, which are attributable mainly to the transition from the stannite crystal structure at x = 0 to the kesterite-like structure near x = 0.13. The detailed analysis of the activation energy in the low-temperature interval permitted estimations of contributions from different crystal phases of the border compounds into the alloy structure at different compositions.
“…There exist only a few articles, where the room temperature resistivity 16, 17, 20 , and its behavior in the high temperature range of 450–550 K 22, 29 have been observed, without any analysis of the data. Probably, the only exclusion is an explicit analysis of the resistivity and magnetoresistance in the kesterite type Cu 2 ZnSn x Ge 1-x Se 4 solid solutions 11 .…”
Section: Introductionmentioning
confidence: 99%
“…In particular, the joint analysis of the resistivity and magnetoresistance data has been widely demonstrated to be an effective method for such a purpose (see e. g. refs 30–38 and references therein), which has been already utilized recently in various kesterite type quaternary compounds 11, 39 .…”
Recent development of the thin film solar cells, based on quaternary compounds, has been focused on the Ge contain compounds and their solid solutions. However, for effective utilization of Cu2ZnGeS4, deeper investigations of its transport properties are required. In the present manuscript, we investigate resistivity, ρ (T), magnetoresistance and Hall effect in p-type Cu2ZnGeS4 single crystals in pulsed magnetic fields up to 20 T. The dependence of ρ (T) in zero magnetic field is described by the Mott type of the variable-range hopping (VRH) charge transfer mechanism within a broad temperature interval of ~100–200 K. Magnetoresistance contains the positive and negative components, which are interpreted by the common reasons of doped semiconductors. On the other hand, a joint analysis of the resistivity and magnetoresistance data has yielded series of important electronic parameters and permitted specification of the Cu2ZnGeS4 conductivity mechanisms outside the temperature intervals of the Mott VRH conduction. The Hall coefficient is negative, exhibiting an exponential dependence on temperature, which is quite close to that of ρ(T). This is typical of the Hall effect in the domain of the VRH charge transfer.
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