Vertical spin transport in semiconductor heterostructures

The Landauer-Buttiker formalism combined with the tight-binding transfer matrix method is employed to model vertical coherent spin transport within magnetization-modulated semiconductor heterostructures based on GaAs. This formalism provides excellent physical description of recent experiments concerning the high tunneling magnetoresistance (TMR) in (Ga,Mn)As-based trilayers and highly polarized spin injection in p-(Ga,Mn)As/n-GaAs Zener diodes. For both the TMR and the Zener spin current polarization, the calculated values compare well with those observed in the experiments, and the formalism reproduces the strong decrease of the observed effects with external bias. We ascribe this decrease to band structure effects. The role played in the spin-dependent tunneling by carrier concentration and magnetic ion content is also studied. (c) 2007 American Institute of Physics.