Résumé
At mesoscopic scale, the variable range hopping can be described by a tunnel effect through a single barrier. We have placed a GaALAs/GaAs HEMT in the quantum Hall regime (high magnetic field and very low temperature) and measured the components of the conductance tensor σxx and σxy. We study the regime of the Shubnikov de Haas peaks and compare it with the same regime in large sample, commonly understood as a VRH regime. We analyse the variation in temperature in the range [0.1K-1K] for kT to scale the fundamental energies, and demonstrate that in the mesoscopic scale, the measured longitudinal conductivity corresponds exactly to the tunneling through a single barrier. We deduce the barrier characteristics by fitting our data with the conductivity of a square tunnel barrier, and we retrieve the characteristic height and length of the bare disorder potential.