Dresden 2006 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 35: II-VI semiconductors III
HL 35.5: Vortrag
Mittwoch, 29. März 2006, 15:30–15:45, POT 151
Carrier-density dependence of the exchange coupling between magnetic ions and conduction band electrons in heavily n-type Zn(1−x)MnxSe and optically pumped Cd(1−x)MnxTe — •M. Lentze1, P. Grabs1, J. Geurts1, K. Rönnburg2, E. Mohler2, and H. Roskos2 — 1Universität Würzburg, Experimentelle Physik III, Am Hubland, 97074 Würzburg — 2Johann Wolfgang Goethe-Universität, Physikalisches Institut, Max-von-Laue-Str. 1, 60438 Frankfurt
Diluted magnetic semiconductors (DMS) like (Zn,Mn)Se and (Cd,Mn)Te show giant magneto-optical effects. These effects originate from the strong s/p-d interaction of the magnetic ions with conduction-band electrons and valence-band holes, which induces a pronounced spin-dependent band-splitting in external magnetic fields. For undoped bulk (Zn,Mn)Se the exchange energy for the electrons amounts to N0α = 260 meV.
We analyzed the doping dependence of the exchange energy N0α of the conduction band electrons for n-doped bulk-like (Zn,Mn)Se samples with doping levels up to n=4·1018 cm−3 and for optically pumped (Cd,Mn)Te. Our analysis was performed by means of spin-flip Raman spectroscopy and by time-resolved Faraday rotation experiments. Our experiments show a distinct decrease of the conduction band exchange energy with increasing n-doping level. For n=4·1018 cm−3, the decrease amounts to 30% with respect to undoped samples. The doping-induced decrease of N0α is explained in terms of the increasing contribution of electronic states with finite q-vector. Their wave functions exhibit an admixture of p-like character.