Stability and diffusion of interstitial and substitutional Mn in GaAs of different doping types

Abstract

We report on ${\ensuremath{\beta}}^{\ensuremath{-}}$ emission channeling experiments on the lattice location and thermal stability of Mn impurities ($l$0.05$%$) in both semi-insulating and heavily $n$-type doped GaAs. In addition to the majority of the Mn impurities substituting for Ga, up to 30$%$ occupy tetrahedral interstitial sites with As nearest neighbors. Whereas the interstitial fraction is stable up to 400${\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}$C, with an activation energy for diffusion of 1.7\char21{}2.3 eV, substitutional Mn diffuses only at $\ensuremath{\sim}$700${\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}$C with an activation energy of $\ensuremath{\sim}$3 eV. By comparing these results to those of recent emission channeling experiments on heavily $p$-type doped GaAs [L. M. C. Pereira et al., Appl. Phys. Lett. 98, 201905 (2011)], we conclude that the observed high thermal stability of the interstitial fraction cannot be ascribed to trapping by charged defects, but is an intrinsic characteristic of isolated interstitial Mn in the low doping regime ($l$0.05$%$ Mn). Compared to ferromagnetic Ga${}_{1\ensuremath{-}x}$Mn${}_{x}$As (few percent Mn), for which a significantly lower activation energy has been reported, these findings motivate a comprehensive assessment of how the thermal stability and the diffusion of interstitial Mn are affected by the Mn concentration.