  We review magneto-optical and magneto-transport effects in GaAs/GaAlAs
heterostructures doped in GaAlAs barriers with donors, providing
two-dimensional electron gas in GaAs quantum wells, and additionally doped with
smaller amounts of acceptors (mostly Be atoms) in the vicinity of 2DEG. One may
also deal with residual acceptors (mostly C atoms). The behavior of such
systems in the presence of a magnetic field differs appreciably from those
doped in the vicinity of 2DEG with donors.
