Defect correlations, metal-insulator transition, and magnetic order in   ferromagnetic semiconductors
  Diluted ferromagnetic III-V semiconductors typically show a high degree of compensation. Compensation is connected to the presence of comparable densities of charged defects of either sign. This naturally leads to the development of strong correlations between defect positions during growth and annealing. We show that these correlations are required to understand the experimentally observed transport and magnetic properties as well as the persistence of the energy gap upon doping with magnetic ions. 
Carsten Timm, Felix von Oppen (Free University Berlin)