  Equilibrium properties of electrons in double-heterojunction
AlGaAs/GaAs\AlGaAs structures are investigated theoretically, using a full
self-consistent numerical method. The transition from single to bilayer
electron systems is discussed for the case of double-junction structures with
varying distance between interfaces. In strong in-plane magnetic fields we
observed the same type of transition accompanied by large effects on the energy
spectra. A new fenomenon in bilayer systems - separability of the energy
dispersion curve in parts corresponding to electrons either in first or second
layer is analyzed in detail. The magnetic field induced variation in the
effective distance between electron layers is compared to the constant layers
separation in standard double-well structures. Due to relatively small and soft
electrostatic barrier between interfaces we expect the van Hove singularity in
the 2D density of states to be easier detectable than in double-well systems.
The cyclotron mass, proportional to the density of states and characterizing
the electron motion in tilted magnetic fields, is calculated as a function of
in-plane magnetic field. The separability of the energy spectra resulting in
tilted cyclotron orbits is demonstrated on a classical picture of an electron
moving in crossed electric and magnetic fields.
