We report on an experimental study of electron transport in submicrometer-wide “wires” fabricated from Si δ-doped GaAs. These quasi-one-dimensional (Q1D) conductors demonstrate the crossover from weak to strong localization with decreasing temperature. On the insulating side of the crossover, the resistance has been measured as a function of temperature, magnetic field, and applied voltage for different values of the electron concentration, which was varied by applying the gate voltage. The activation temperature dependence of the resistance has been observed with the activation energy close to the mean energy spacing of electron states within the localization domain. The study of nonlinearity of the current-voltage characteristics provides information on the distance between the critical hops that govern the resistance of Q1D conductors in the strong localization (SL) regime. We observe the exponentially strong negative magnetoresistance; this orbital magnetoresistance is due to the universal magnetic-field dependence of the localization length in Q1D conductors. The method of measuring the single-particle density of states (DOS) in the SL regime has been suggested. Our data indicate that there is a minimum of DOS at the Fermi level due to the long-range Coulomb interaction.

• Received 7 May 1998

DOI:https://doi.org/10.1103/PhysRevB.58.8009