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

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

FZU 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 III-V family: Internal reference rule

FZU Lattice constant: Vegard’s law

FZU Tight-binding model

FZU Tight-binding model – cont.

FZU Tight-binding model – cont.

FZU T C : LDA+U calculations mean-field calculations for 5% and 10% Mn

FZU Range of exchange coupling

FZU Mn interstitials: formation energies Formation energies E s,i (x s,x i ) of Mn Ga and Mn I as functions of partial concentrations x s and x i. Balanced state: E s (x s,x i ) = E i (x s,x i ).

FZU Ga(As,P): Mn Ga vs Mn I

FZU (Al,Ga)As: Mn Ga, Mn Al vs. Mn I

FZU Substitutional vs.interstitial Mn

FZU Summary Strength of p-d hybridization is more important for T C 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 T C in (Ga,Mn)(As,P) No improvement expected in (Al,Ga,Mn)As Preferential formation of Mn I in (Al,Ga)As