sp-d exchange coupling in Mn doped GaN and ZnO studied by

sp-d exchange coupling in Mn doped GaN and ZnO studied by
magnetospectroscopy
J. Suffczyński1, A. Grois2, W. Pacuski1, P. Kossacki1, A. Golnik1, J. A. Gaj1,
D. Ferrand3, J. Cibert3, Y. Dumont4, E. Chikoidze4, C. Deparis6, C. Morhain6,
A. Navarro-Quezada2, B. Faina2, T. Devillers2, A. Bonanni2, T. Dietl1,6
1
2
Inst. of Exp. Physics, Faculty of Physics, University of Warsaw, Warsaw, Poland
Institut für Halbleiter- und Festkörperphysik, J. Kepler University, Linz, Austria
3
Laboratoire Louis Néel, CNRS-Universite J. Fourier, Grenoble, France
4
CNRS-Université de Versailles, Meudon, France, 5 CNRS, Valbonne, France
6
Institute of Physics, Polish Academy of Sciences, Warsaw, Poland; Institute of
Theoretical Physics, Faculty of Physics, University of Warsaw, Warsaw, Poland
Presented magneto-optical studies of excitons in paramagnetic Ga1−xMnxN
(x < 0.01) [1] and Zn1−xMnxO (x < 0.03) [2] layers are stimulated by the recent
theoretical findings [3,4] indicating that (i) the strong p-d coupling, specific to
nitrides [5] and oxides [6], leads to a breakdown of the virtual crystal and molecular
field approximations, which renormalizes the spin splitting of the valence band states
[3]; (ii) the spin splitting of the conduction band is strongly affected by the exchange
coupling of electrons to holes bound by Mn acceptors [4].
Experiment shows that in agreement with the prediction [3], the band gap
energy increases with the Mn ion concentration [1,2]. Moreover, the apparent p-d
exchange energy N0β describing valence band splitting is found to be much reduced
and ferromagnetic [1,2]. We find N0β(app) = +0.8 ± 0.2 eV [1] and +0.5 ± 0.15 eV [2]
for Ga1−xMnxN and Zn1−xMnxO, respectively. In agreement with [4], the value of the
N0α describing conduction band splitting in Ga1−xMnxN is found to be small, N0α =
0.0 ± 0.1 eV [1]. Our results [2] point to the reverse ordering of the valence band
subbands in ZnO as compared to GaN. Furthermore, we discuss the origin of
mutually opposite circular polarizations of excitonic reflectivity and
photoluminescence, found for Zn1−xMnxO in the magnetic field [2].
[1] J. Suffczyński et al., Physical Review B 83, 094421 (2011).
[2] W. Pacuski et al., Physical Review B 84, 035214 (2011).
[3] T. Dietl, Phys. Rev. B 77, 085208 (2008).
[4] C. Śliwa and T. Dietl, Phys. Rev. B 78, 165205 (2008).
[5] J. I. Hwang et al., Phys. Rev. B 72, 085216 (2005).
[6] J. Okabayashi et al., J. Appl. Phys. 95, 3573 (2004).