Raising TC of ferromagnetic semiconductors through doping control: The case of GaMnAs

The difficulty of increasing the Curie temperature TC of magnetic semiconductors such as (Ga,Mn)As above the room temperature is related to the p-type doping bottleneck in this system, which has hindered the further development of dilute magnetic semiconductors. To overcome the p-type doping bottleneck, we investigate the doping properties of Mn in GaAs with hybrid functional calculations and propose strategies that can improve the p-type dopability in (Ga,Mn)As. We find that tensile strain and high temperature quenching are effective approaches to enhance p-type doping in epitaxial (Ga,Mn)As. The tensile strain applied, e.g., by the substrate with a larger lattice constant can decrease the formation energy of the substitutional dopant MnGa−, which is an acceptor with large size, and increase that of interstitial Mni2+, which is a small size compensating donor, thus improving the p-type dopability. The high temperature quenching also can achieve higher hole density by limiting the formation of compensating interstitial Mn. We suggest that the combination of these two schemes would effectively enhance the p-type dopability and further raise the Curie temperature TC of (Ga,Mn)As.