Diffusion of Mn interstitials in (Ga,Mn)As epitaxial layers

TL;DR

This study investigates how Mn interstitials diffuse out of (Ga,Mn)As layers during annealing, revealing that internal electric fields significantly influence the diffusion process and magnetic property improvements.

Contribution

It combines experimental techniques with numerical modeling to show the impact of internal electric fields on Mn interstitial diffusion in (Ga,Mn)As layers.

Findings

Mn interstitials out-diffuse during annealing

Internal electric fields affect diffusion behavior

Surface Mn-rich layer formation inhibits further out-diffusion

Abstract

Magnetic properties of thin (Ga,Mn)As layers improve during annealing by out-diffusion of interstitial Mn ions to a free surface. Out-diffused Mn atoms participate in the growth of a Mn-rich surface layer and a saturation of this layer causes an inhibition of the out-diffusion. We combine high-resolution x-ray diffraction with x-ray absorption spectroscopy and a numerical solution of the diffusion problem for the study of the out-diffusion of Mn interstitials during a sequence of annealing steps. Our data demonstrate that the out-diffusion of the interstitials is substantially affected by the internal electric field caused by an inhomogeneous distribution of charges in the (Ga,Mn)As layer.