Spin-polarized carrier populations in diluted magnetic semiconductor quantum well structures (abstract)

Abstract

Diluted magnetic semiconductors (DMS) offer the opportunity to significantly alter heterojunction band offsets via an applied magnetic field due to the large Zeeman splittings (enhanced g-factors) they exhibit. We have previously reported field-dependent spatial spin segregation of holes in DMS quantum well structures1,2 which resulted from the small band offset and large spin splitting exhibited by the valence band. We report here the growth of tailored Zn1-xFexSe/ZnSe quantum well structures in which both electrons and holes are spatially segregated according to their spin, resulting in spin-polarized carrier populations in the barriers and wells: the spin-down carriers are localized in the Zn1-xFexSe barriers, while the spin-up carriers are localized in the wells. Both single and multiple quantum well samples were grown by molecular-beam epitaxy on GaAs(001) substrates with 100 Å barriers and wells. The heavy-hole excitonic transitions were studied with magnetoreflectivity at T=4.2 K and fields up to 8 T. The magnetoreflectivity data show that both (-3/2→-1/2) and (3/2→1/2) excitonic transitions are of equal intensity and spatially direct (type I), with the former showing the strong field dependence expected for localization in the magnetically active barriers.