Strain effect on the diffusion of interstitial Mn in GaAs

The influence of external strain on the diffusion barriers of interstitial Mn in GaAs is studied using the first-principles calculations within the density functional theory. The diffusion barrier changes with strain in different manners: linear on the tensile strain and nonlinear on compressive strain, in contrast to the linear behavior of the continuum elastic model. The discrepancy between the continuum elastic model and the results of the first-principles method is attributed to the energy-level crossing caused by strain. Moreover, we find that the external strain can not only effectively change the diffusion barrier (even to zero, at certain strain), but also the position of saddle points along the migration path. Our finding provides an alternative way to reduce the population of interstitial Mn in GaAs, thus correspondingly to increase the Curie temperature of this system. (paper)