The results on the measurement of electrical conductivity and magnetoconductivity of a GaAs double quantum well between 0.5 and 1.1 K are reported. The zero magnetic-field conductivity is well described from the point of view of contributions made by both the weak localization and electron-electron interaction. At low field and low temperature, the magnetoconductivity is dominated by the weak localization effect only. Using the weak localization method, we have determined the electron dephasing times and tunneling times t . Concerning tunneling, we concluded that t presents a minimum around the balance point; concerning dephasing, we observed an anomalous dependence on temperature and conductivity ͑or elastic mean free path͒ of . This anomalous behavior cannot be explained in terms of the prevailing concepts for the electron-electron interaction in high-mobility two-dimensional electron systems.

In this work we studied the transport properties of a two-dimensional electron gas (2DEG) in a series of GaAs∕InGaAs delta-modulation-doped quantum wells, in which an InAs layer was located in the vicinity of the electron channel. We observed that, even after illumination, all samples exhibited a total free-electron concentration slightly lower than the one measured in a reference sample (without the InAs layer), an effect that was attributed to the transfer of carriers from the 2DEG to the surface states. Our data also provided evidence that strain fields in and around the quantum dots act as additional scattering sources for the 2DEG.

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We report a comprehensive study of weak-localization and electron-electron interaction effects in a GaAs/InGaAs two-dimensional electron system with nearby InAs quantum dots, using measurements of the electrical conductivity with and without magnetic field. Although both the effects introduce temperature dependent corrections to the zero magnetic field conductivity at low temperatures, the magnetic field dependence of conductivity is dominated by the weak-localization correction. We observed that the electron dephasing scattering rate τφ−1, obtained from the magnetoconductivity data, is enhanced by introducing quantum dots in the structure, as expected, and obeys a linear dependence on the temperature and elastic mean free path, which is against the Fermi-liquid model.

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