We present the characterization of the band structure of GaAs/AlAs quantum-wire 1D superlattices performed by magnetophonon resonance with pulsed magnetic fields up to 35 T. The samples, generated by the atomic saw method from original quantum-well 2
D superlattices, underwent substantial modifications of their energy bands built up on the X-states of the bulk. We have calculated the band structure by a finite element method and we have studied the various miniband structures built up of the masses m_t and m_l of GaAs and AlAs at the point X. From an experimental point of view, the main result is that in the 2D case we observe only resonances when the magnetic field B is applied along the growth axis whereas in the 1D case we obtain resonances in all magnetic field configurations. The analysis of the maxima (or minima for B // E) in the resistivity rho_xy as a function of B allows us to account, qualitatively and semi-quantitatively, for the band structure theoretically expected.
We use both Quantum Hall and Shubnikov de Haas experiments at high magnetic field and low temperature to analyse broadening processes of Landau levels in a delta-doped 2D quantum well superlattice and a 1D quantum wire superlattice generated from the
first one by controlled dislocation slips. We deduce first the origin of the broadening from the damping factor in the Shubnikov de Haas curves in various configurations of the magnetic field and the measured current for both kinds of superlattice. Then, we write a general formula for the resistivity in the Quantum Hall effect introducing a dephasing factor we link to the process of localization.
The atomic saw method uses the passage of dislocations in two-dimensional (2D) quantum-well superlattices to create periodic slipping layers and one-dimensional (1D) quantum wire superlattices. The effects of this space structuring of the samples on
the allowed energies are analysed in the case of GaAs d-doped superlattices. If they are sufficiently large, the various minigaps appearing in the 1D band structure could be responsible for the presence of negative differential resistance (NDR) with high critical current in these systems. The purpose is to determine the evolution of the minigaps in terms of the sample parameters and to obtain the means to determine both the 2D and 1D structural characteristics where NDR could appear.
Quantum wire superlattices (1D) realized by controlled dislocation slipping in quantum well superlattices (2D) (atomic saw method) have already shown magnetophonon oscillations. This effect has been used to investigate the electronic properties of su
ch systems and prove the quantum character of the physical properties of the wires. By cooling the temperature and using pulsed magnetic field up to 35 T, we have observed both quantum Hall effect (QHE) and Shubnikov de Haas (SdH) oscillations for various configurations of the magnetic field. The effective masses deduced from the values of the fundamental fields are coherent with those obtained with magnetophonon effect. The field rotation induces a change in the resonance frequencies due to the modification of the mass tensor as in a (3D) electron gas. In view the QHE, the plateaus observed in rho_yz are dephased relatively to rho_zz minima which seems to be linked to the dephasing of the minima of the density of states of the broadened Landau levels.
