One-dimensional character of miniband transport in doped GaAs/AlAs superlattices

Evidence of the crucial role of random fluctuations of the well size in vertical transport in doped GaAs/AlAs superlattices with broad minibands has been obtained by both Fourier-transform reflection spectroscopy and C-V measurements. It turned out that even monolayer fluctuations of the periodicity, or random fluctuations of the impurity potentials, which are unavoidable, can cause a partial localization of electrons providing one-dimensional conducting channels where the periodicity is conserved, and through which the electron transport across the superlattice would occur. This was found to be the reason why, instead of the constant vertical conductivity (independent of the electron density) predicted by the theory to occur when the Fermi energy exceeds the miniband width, a drop of the conductivity giving a metal-to-dielectric phase transition was observed.