Theory of Mn_Ga-H and other acceptor-H complexes in GaAs

Mn doped GaAs is a potentially important material for the construction of dilute-ferromagnetic semiconducting devices. Due to the Mn ions representing both the magnetic ion and acceptor, the addition of hydrogen to selectively passivate Mn ions while retaining the magnetic properties has been suggested. However, the location of the H atom in the defect remains to be determined unambiguously. We present the results of density-functional calculations regarding the structure, vibrational and dilatation effects of X_Ga and X_Ga-H complexes for X=Mn, Be, Mg, and Zn. In all cases, H passivates the acceptor and energetically favors the bond-centered site. Passivated Mn_Ga is found to have a high-spin configuration of S=5/2.