Ferromagnetism mediated by the upper Hubbard band in selectively doped GaAs/AlGaAs structures

We consider in detail the indirect exchange between Mn ions imbedded to GaAs/AlGaAs quantum wells where the barriers are doped by acceptor impurity supported by the carriers of the upper Hubbard band supplied by barriers acceptors. A special attention is paid to an interplay between strong delocalization of the carriers within the upper Hubbard band (allowing exchange between well separated ions) and relatively weak coupling of these carriers with Mn ions. It is shown, that, despite of the latter factor, the values of Curie temperatures can for such structures be as high as room temperatures.