Schematic of the layer structure of the QDC samples grown by MBE. The δ-doping was located in the middle of each GaAs spacer layer only for the last 5 periods of growth. Three samples with different doping were prepared: sample , sample , and sample .
(a) μm2 AFM topography image of QDC sample C. The chains are aligned along the crystallographic direction; (b) μm2 AFM image of the same sample; statistical distribution with Gaussian fits of the (c) QD height; (d) distance between QDs, din , within the chains (peak-to-peak) measured along direction; and (e) distance between neighboring chains, dbc , measured peak-to-peak; (f) hall bar structure used for electrical characterization with a channel width of 25 μm.
Mobility versus temperature for . (a) Across the chains and (b) along the chains, both showing the effects of changing the number of neighbors involved in hopping. (c) Across the chain, for hops between the 3rd closest neighbors, varying Δ. (d) Along the chain, for hops between the 10th closest neighbors, varying Δ.
Anisotropy ratio as a function of both temperature and Δ. The upper panel shows the complete 3D plot of this surface. The lower panel shows temperature profiles at different values of Δ. With the narrow vertical scale here, it is easy to see the evolution of the maxima of the anisotropy ratio as Δ increases.
(a) The Hall mobilities and (b) the electron sheet densities measured as a function of temperature for samples A, B, and C along the QDCs ( direction, solid symbols) and across the QDCs ( direction, open symbols); (c) anisotropy as function of temperature and remote doping for samples A, B, and C. The inset shows a schematic band diagram in the (100) plane for (along QDCs) and  (across QDCs) crystallographic directions as well as the density of states diagrams.
(a) Sheet resistance as a function of inverse temperature.
versus log(T). (a) and (b) along and across QD chain, respectively, with different number of hopping neighbors. The 1D Mott behavior (x = 1/2) is shown by solid line. (c) and (d) along and across QD chain, respectively, where Δ is varying. (e) and (f) are experimental data.
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