Lattice Expansion of (Ga,Mn)As: The Role of Substitutional Mn and of the Compensating Defects

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We apply the density-functional technique to determine the lattice constant of GaAs supercells containing MnGa, Mnᵢnt, and AsGa impurities, and use a linear interpolation to describe the dependence of the lattice constant a of Ga₁₋ₓMnₓAs on the concentrations of these impurities. The results of the supercell calculations confirm that MnGa does not contribute to the lattice expansion. The increase of a is due to both Mnᵢnt and AsGa, that are both created in the as-grown (Ga,Mn)As in proportion to x, and that are most probably present in a remarkable amount also in the best annealed materials.