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

TL;DR

This study uses density-functional calculations to analyze how substitutional Mn and compensating defects influence the lattice expansion in (Ga,Mn)As, revealing that Mn interstitials and As antisites, not substitutional Mn, cause lattice increase.

Contribution

It provides a detailed computational analysis of impurity effects on lattice parameters, clarifying the roles of different defects in (Ga,Mn)As.

Findings

Mn_Ga does not cause lattice expansion.

Mn_int and As_Ga contribute to lattice increase.

Compensating defects are prevalent even in annealed samples.

Abstract

We apply the density-functional technique to determine the lattice constant of GaAs supercells containing Mn_Ga, Mn_int, and As_Ga impurities, and use a linear interpolation to describe the dependence of the lattice constant a of Ga_{1-x}Mn_xAs on the concentrations of these impurities. The results of the supercell calculations confirm that Mn_Ga does not contribute to the lattice expansion. The increase of a is due to both Mn_int and As_Ga, 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.