We have measured the temperature (2.9 K < T < 50 K) and magnetic field (0 T < B < 9 T) dependences of longitudinal and Hall resistivities for HgCdTe/HgTe/HgCdTe system with HgTe quantum well width of 20.3 nm. The activation analysis of the experimental magnetoresistivity traces has been used as a quantitative tool to probe inter-Landau level distances. The activation energies were determined from the temperature dependence of the longitudinal resistivity in the regions of quantized Hall plateaus (for the filling factors ν of 1, 2 and 3) and the indications of the large values of the g factor ≅ 30-75 were found.

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Abstract. We have measured the temperature (0.1 ≤ T ≤ 15 K) and magnetic field (0 ≤ B ≤ 32 T) dependences of longitudinal and Hall resistivities for the p-Ge0.93Si0.07/Ge multilayers with different Ge layer widths 10 ≤ dw ≤ 38 nm and hole densities ps = (1÷5)·10 15 m -2 . An extremely high sensitivity of the experimental data (the structure of magnetoresistance traces, relative values of the inter-Landau-level (LL) gaps deduced from the activated magnetotransport etc) to the quantum well (QW) characteristics has been revealed in the cases when the Fermi level reached the second confinement subband. The background density of states (5÷10)·10 14 m -2 meV -1 deduced from the activation behavior of the magnetoresistance was too high to be attributed to the LL tails, but may be accounted for within a smooth random potential model. The hole gas in the Ge quantum well was found to separate into two sublayers for dw > ~35 nm and ps ≈ 5·10 15 m -2 . Concomitantly the positive magnetoresistance emerged in the weakest fields, from which different mobilities in the sublayers were deduced. A model is suggested to explain the existence of the plateaux close to the fundamental values in a system of two parallel layers with different mobilities.

The effective g-factor in In0.53Ga0.47As/In0.52Al0.48As quantum well investigated by magnetotransport measurement J. Appl. Phys. 113, 033704 (2013); 10.1063/1.4776236Electron dephasing scattering rate in two-dimensional GaAs/InGaAs heterostructures with embedded InAs quantum dotsThe temperature and magnetic-field dependence of the components of the conductivity and resistivity tensors are calculated with the quantum corrections due to the weak localization effect and electron-electron interaction taken into account in the diffusion and ballistic regimes. The corrections to the conductivity from the weak localization and electron-electron interaction and also the influence of spin and oscillation effects are taken into account by a renormalization of the transport relaxation time of the electron momentum, with the result that the Drude conductivity becomes temperature dependent. A calculation of the components of the conductivity and resistivity tensors is carried out with the use of the theoretical values of the parameters of the theory of quantum corrections, which are determined solely by the values of the carrier density and mobility of a particular sample. The results of the calculation are compared with experimental results for two-dimensional n-InGaAs/ GaAs structures with double quantum wells. It is shown that taking only the quantum corrections into account with the theoretical values of the parameters does not permit even a qualitative description of experiment, and it is therefore necessary to take additional temperature-dependent contributions to the Drude conductivity into account.

In a two-dimensional (2D) hole system (multilayer p-Ge/Ge1−xSix) heterostructure with conductivity σ≈e2/h at low temperatures (T≈1.5 K) a transition from the insulator phase (dσ/dT&gt;0) to a “metallic” phase (dσ/dT&lt;0) is observed as the temperature is lowered, behavior that is in qualitative agreement with the predictions of the Finkelstein theory. In a magnetic field B perpendicular to the plane of the 2D layer one observes positive magnetoresistance depending only on the ratio B/T. We attribute the positive magnetoresistance effect to the suppression of the triplet channel of Fermi-liquid electron–electron interaction by the magnetic field owing to the strong Zeeman splitting of the hole energy levels.