In the course of the studies on the GaAs/AlGaAs heterostructures in the quantum Hall (QH) regime it has been shown that in magnetic fields H corresponding to the Hall's plateau, when the electrons are localized, the acoustoelectric effects are governed by the hf hopping conductivity. The latter is not equivalent to the dc conductivity and is a complex quantity. Both real and imaginary parts are obtained by simultaneous measurements of the attenuation and velocity change of the surface acoustic wave (SAW). This is a pioneering result that allows us to successfully promote a new scientific approach to the study of the localized states of the two-dimensional electrons in the QH-regime [1]. It should be noticed that dc-studies of these objects could not be performed at the Hall's plateau centre, the dc conductivity at the corresponding H=0.

        HF-conductivity in the modulation-Si-doped GaAs/AlGaAs heterostructures has been studied by the acoustoelectric method also. It has been shown that in the QH regime the hf hopping conductivity of the 2DEG layer is effectively shunted by that of the AlGaAs doping region. A method to separate these two contributions to the hf-conductivity in the QH regime has been put forward, and the localization length in the corresponding H evaluated.

        It has been observed that both the hf hopping conductivity and the carrier density in these samples depend on the rate of the sample cooling, illumination, and stress. An energy threshold there exists at which the frozen hf hopping photoconductivity takes place. This result is attributed to the so-called DX-centers [2].

        For the first time, this contactless acoustic method was applied for the monitoring of the Si/SiGe heterostructures in the IQHE regime. The absorption and velocity shift of the SAW have been measured in the IQHE regime.

   Since neither Ge, nor Si are piezoelectrics, the only way to measure the acoustoelectric effects in the systems is a hybrid method when a SAW propagates along a surface of a piezoelectric, while the sample is placed on its surface. In this case only the electric field of the SAW penetrates into the Si/SiGe sample.

     Dense arrays of Ge quantum dots in Si host were studied using the acoustical method. The measured temperature dependencies of the DC conductance of the same samples evidence the variable range hopping (VRH) in the Coulomb gap regime.

   Quantum oscillations of SAW attenuation and velocity in the GaAs/AlGaAs heterostructures in the case of spin-splitted Landau bands have been observed and investigated. It allowed one to obtain the electronic g-factor value for the 2DEG, which appeared to be near an order higher than the g-factor for the bulk GaAs [3, 4].

       All the results cited above confirm the ability of the team to perform acoustoelectric measurements in the nanosystems of different type.

        Experimental Technique in Use: He³ low temperature setup T=0.3-4.2K, magnetic fields up to 7T. Operating frequencies f=30-300MHz.