Mn-doped Ga(As,P) and (Al,Ga)As ferromagnetic semiconductors
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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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Outline

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


Outline

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


Motivation

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


Iii v family internal reference rule

III-V family: Internal reference rule

FZU 7.11.2006


Outline

Lattice constant: Vegard’s law

FZU 7.11.2006


Outline

Tight-binding model

FZU 7.11.2006


Outline

Tight-binding model – cont.

FZU 7.11.2006


Outline

Tight-binding model – cont.

FZU 7.11.2006


T c lda u calculations

TC: LDA+U calculations

mean-field calculations for 5% and 10% Mn

FZU 7.11.2006


Range of exchange coupling

Range of exchange coupling

FZU 7.11.2006


Mn interstitials formation energies

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


Ga as p mn ga vs mn i

Ga(As,P): MnGa vs MnI

FZU 7.11.2006


Al ga as mn ga mn al vs mn i

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

FZU 7.11.2006


Substitutional vs interstitial mn

Substitutional vs.interstitial Mn

FZU 7.11.2006


Summary

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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