Virtual Anderson transition in a narrow impurity band of doped $p$-GaAs/AlGaAs layers

In highly doped uncompensated layers of p-GaAs/AlGaAs quantum wells, activation conduction with low activation energies is observed at low temperatures and this conduction is not explained by known mechanisms (ε₄ conduction). Such behavior is attributed to the delocalization of electron states near the maximum of a narrow impurity band in the sense of the Anderson transition. In this case, conduction is implemented due to the activation of minority carriers from the Fermi level to the indicated delocalized-state band.