ONE-DIMENSIONAL CHARACTER OF MINIBAND TRANSPORT IN DOPED GAAS ALAS SUPERLATTICES/

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