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Abstract

We have investigated the magnetoresistance of strongly
asymmetric double-well structures formed by a thin Al0.3Ga0.7As
barrier grown far from the interface in the GaAs buffer of
standard heterostructures. In magnetic fields oriented parallel
to the electron layers, the magnetoresistance exhibits an
oscillation associated with the depopulation of the higher
occupied subband and with the field-induced transition into a
decoupled bilayer. In addition, the increasing field transfers
electrons from the triangular to rectangular well and, at high
enough field value, the triangular well is emptied.
Consequently, the electronic system becomes a single layer
which leads to a sharp step in the density of electron states
and to an additional minimum in the magnetoresistance curve.
(C) 2002 Elsevier Science B.V. All rights reserved.