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Mn-doped Ga(As,P) and (Al,Ga)As ferromagnetic semiconductors J.Mašek, J. Kudrnovský, F.Máca, T.Jungwirth, Jairo Sinova, A.H.MacDonald. Outline. Motivation Enhanced Curie temperature in mixed hosts Defects: substitutional vs. interstitial Mn in the Ga(As,P) and (Al,Ga)As Summary. Motivation.

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  1. Mn-doped Ga(As,P) and (Al,Ga)As ferromagnetic semiconductorsJ.Mašek, J. Kudrnovský, F.Máca, T.Jungwirth,Jairo Sinova, A.H.MacDonald FZU 7.11.2006

  2. Outline • Motivation • Enhanced Curie temperature in mixed hosts • Defects: substitutional vs. interstitial Mn in the Ga(As,P) and (Al,Ga)As • Summary FZU 7.11.2006

  3. Motivation • Wider bandgap than in GaAs Mn d- states closer to the valence band edge  • Mn acceptor level deeper in VB and more localized extend of exchange coupling • Smaller lattice constant of GaP enhanced p-d hybridization FZU 7.11.2006

  4. III-V family: Internal reference rule FZU 7.11.2006

  5. Lattice constant: Vegard’s law FZU 7.11.2006

  6. Tight-binding model FZU 7.11.2006

  7. Tight-binding model – cont. FZU 7.11.2006

  8. Tight-binding model – cont. FZU 7.11.2006

  9. TC: LDA+U calculations mean-field calculations for 5% and 10% Mn FZU 7.11.2006

  10. Range of exchange coupling FZU 7.11.2006

  11. Mn interstitials: formation energies • Formation energies Es,i (xs,xi) of MnGa and MnI as functions of partial concentrations xs and xi . • Balanced state: Es(xs,xi) = Ei(xs,xi) . FZU 7.11.2006

  12. Ga(As,P): MnGa vs MnI FZU 7.11.2006

  13. (Al,Ga)As: MnGa , MnAl vs. MnI FZU 7.11.2006

  14. Substitutional vs.interstitial Mn FZU 7.11.2006

  15. Summary • Strength of p-d hybridization is more important for TC high than band structure effect • The range of exchange coupling in (Ga,Mn)(As,P) unchanged for less than 50% P • Suppressed formation of MnI in (Ga,Mn)(As,P) • Remarkable increase of TC in (Ga,Mn)(As,P) • No improvement expected in (Al,Ga,Mn)As • Preferential formation of MnI in (Al,Ga)As FZU 7.11.2006

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