High Ferromagnetic Transition Temperature (172K) in Mn delta-doped GaAs   with p-type Selective Doping
  We have found high ferromagnetic transition temperature in Mn delta-doped GaAs-based heterostructures grown on GaAs(001) substrates by molecular beam epitaxy. A 0.3 ML Mn d-doped GaAs samples showed high resistivity at low temperature and did not show a ferromagnetic behavior. However, in a selectively doped heterostructure (Mn delta-doped GaAs / Be-doped AlGaAs), where holes were supplied from the Be-doped AlGaAs layer, clear ferromagnetic order was observed. The ferromagnetic transition temperature of the selectively doped heterostructure was as high as 172K with suitable low-temperature (LT) annealing treatment. 
Ahsan M. Nazmul, S. Sugahara and M. Tanaka