The absorption coefficient for surface acoustic waves in a piezoelectric insulator in contact with a GaAs/AlGaAs heterostructure (with two-dimensional electron mobility µ = 1.3 × 10 5 cm 2 /V · s) at T =4.2K) via a small gap has been investigated experimentally as a function of the frequency of the wave, the width of the vacuum gap, the magnetic field, and the temperature. The magnetic field and frequency dependencies of the high-frequency conductivity (in the region 30-210 MHz) are calculated and analyzed. The experimental results can be explained if it assumed that there exists a fluctuation potential in which current carrier localization occurs. The absorption of the surface acoustic waves in an interaction with two-dimensional electrons localized in the energy "tails" of Landau levels is discussed.

No abstract

Low-magnetic-field magnetoresistance of a two-dimensional electron gas (2DEG) in a triangular quantum well at a single In 0.53 Ga 0.47 As-InP heterointerface has been studied. It was shown that the spin-orbit relaxation plays a significant role in the low-field magnetoresistivity in a wide range of 2DEG densities (1.8-5.5) × 10 11 cm −2 . Analysis shows that both cubic and linear terms in the wavevector must be taken into account in spin splitting to describe experimental results. The linear term is mainly related to the asymmetry of the quantum well (Rashba term). Analysis of the density dependence of the spin-orbit interaction rate permits separation of the spin splittings related to the lack of inversion of the crystal and to the asymmetry of quantum well and determination of the spin splitting parameters for 2D electrons in asymmetric In 0.53 Ga 0.47 As quantum wells.

Shubnikov-de Haas oscillations corresponding to the spin-resolved Landau levels of the two-dimensional electron gas at an In 0.53 Ga 0.47 As-InP heterointerface were studied in wide ranges of magnetic fields (up to 22 T) and tilt angles. Dependences of the spin splitting s on the parallel component of magnetic field were investigated for half-filled Landau levels 0↑, 1↓, 1↑, 2↓ and 2↑. The exchange interaction was shown to be strongly dependent on the broadening and overlapping of adjacent Landau levels. On the basis of this model, the experimental magnetic field dependences of s were described. As a result, the absolute value of bare g-factor g 0 = 2.9, exchange energy E x = 30 meV and Landau level broadening = 7-11 meV were obtained.

The energy relaxation in two-dimensional electron gas in In0.53 Ga0.47 As/ InP has been studied in a wide range of electron temperatures (from 0.1 to 10 K). The energy loss rate of electrons is controlled by the interaction of electrons with the piezoelectric potential of acoustic phonons. The value of the piezoelectric constant for InGaAs lattice-matched to InP is deduced from theoretical fits of the experimental data: h14 = (1.1±0.1) x 10 7