3d transition metal diffusion in diluted magnetic semiconductors prepared by pulsed laser processing

3d transition metal diffusion in diluted magnetic semiconductors prepared by pulsed laser processing

Bürger, D.; Seeger, M.; Zhou, S.; Skorupa, W.; Schmidt, H.

High dopant concentrations are often a prerequisite condition for the realization of semiconductors with new functionalities. For example, magnetic dopants can be used to fabricate ferromagnetic semiconductors (FMS) [1] or intermediate band semiconductors for solar cells [2, 3]. The main problem for processing these materials is the very low solubility of magnetic dopants in elementary and III-V semiconductors. Therefore, thermodynamical non-equilibrium conditions have to be applied to overcome these limits. Thereby, the diffusion path during processing has to be as short as possible to reduce clustering processes which would result in a deactivation of dopants.
The diffusion barrier Q of standard shallow donor or acceptor dopants in the solid phase
is generally high which results in very low diffusion coefficients. Therefore, during the fast cooling process after PLA, diffusion or hopping of such shallow dopant atoms in recrystallized Si and GaAs has not been considered in detail and no models were developed which quantify interdiffusion processes of dopants for materials with large bulk diffusion barriers Q. However, 3d transition metal dopants in the most important semiconductors have relatively small bulk diffusion barriers Q that result in higher diffusion rates as compared to standard shallow donors. Therefore, the usual assumption that dopants remain fixed on their initial position during PLA processing has to be verified for each type of magnetic dopant in semiconductor spintronics materials.
In this work, we perform a Monte Carlo Study on a three-dimensional diffusion model to evaluate the kinetics of initial clustering in a simple cubic host:dopant system. In a second step, the temperature quenching process during PLA was calculated for the materials GaAs and Si and conclusions about diffusion and clustering of typical 3d transition metal dopants can be drawn with respect to the PLA parameters. For Mn in GaAs we also consider declustering effects that have to be included for strongly diffusing dopants like Mn in Si.

[1] T. Dietl, H. Ohno, F. Matsukura, J. Cibert, and D. Ferrand, Science 287, 1019 (2000).
[2] A. Luque and A. Marti, Phys. Rev. Lett. 78, 5014 (1997).
[3] J. Olea, M. Toledano-Luque, D. Pastor, G. Gonzáles-Díaz, and I. Mártil, J. Appl. Phys. 104, 016105 (2008).

Keywords: nanoscale clustering; diffusion; diluted magnetic semiconductor

  • Poster
    subtherm 2011, 24.-27.10.2011, Dresden, Deutschland

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Publ.-Id: 16422