Observation of the anisotropic hopping conductivity of p-CdSb in a magnetic field

The resistivity of the anisotropic semiconductor p-CdSb is investigated in a wide temperature range of T = 1.9 - 300 K in pulsed magnetic fields up to B = 25 T. Two not intentionally doped single-crystalline samples oriented along the crystallographic axes [100] (no. 1) and [010] (no. 2) are used for measurements of the resistivity, ρ, in transversal magnetic field configuration. Below T ≅ 8 K the resistivity follows the laws lnρ ∼ CB2 for BBc, where the coefficients C and S do not depend on T, and Bc ≅ 5 - 7.5 T. These are characteristics of nearest-neighbour hopping conductivity. The coefficients C and S depend on the direction of B, and their ratios agree completely with the values calculated with the components of the hole effective mass. The acceptor concentrations, N1 ≅ 4.3 x 1016cm-3 and N2 ≅ 7.6 x 1016cm-3 for no. 1 and no. 2, respectively, are relatively close to the critical value of the metal-insulator transition (MIT), Nc ≅ 1.2 x1017cm-3. This leads to enhancement of the mean localization radii, a1* ≅ 78 Angst. in no. 1 and a2* ≅ 126 Angst. in no. 2, with respect to the value of a0* ≅ 50 Angst. far from the MIT determined by an asymptote of the wavefunction at a large distance from the impurity centre