Abstract
The low-temperature 2D variable range hopping conduction over the states of the upper Hubbard band is investigated in detail for the first time in multilayered Be-doped p-type GaAs/AlGaAs structures with quantum wells of 15-nm width. This situation was realized by doping the layer in the well and a barrier layer close to the well for the upper Hubbard band (A+ centers) in the equilibrium state filled with holes. The conduction was of the Mott hopping type in the entire temperature range (4−0.4 K). The positive and negative magnetoresistance branches as well as of non-Ohmic hopping conduction at low temperature are analyzed. The density of states and the localization radius, the scattering amplitude, and the number of scatterers in the upper Hubbard band are estimated. It is found that the interference pattern of phenomena associated with hopping conduction over the A+ band is qualitatively similar to the corresponding pattern for an ordinary impurity band, but the tunnel scattering is relatively weak.
Published Version
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