  The electronic structure of Mn doped GaAs and GaN have been examined within a
multiband Hubbard model. By virtue of the positioning of the Mn d states, Mn
doped GaAs is found to belong to the p-d metal regime of the
Zaanen-Sawatzky-Allen phase diagram and its variants while Mn doping in GaN
belongs to the covalent insulator regime. Their location in the phase diagram
also determines how they would behave under quantum confinement which would
increase the charge transfer energy. The ferromagnetic stability of Mn doped
GaAs, we find, increases with confinement therefore providing a route to higher
ferromagnetic transition temperatures.
