Self-consistent ballistic and diffusive spin transport across interfacial resistances in a hybrid ferromagnet-semiconductor trilayer

Abstract

Spin dependent interfacial resistance (RI) is crucial for achieving high spin injection efficiency from a ferromagnetic (FM) metal into a semiconductor (SC). We present a self-consistent model of spin transport across interfacial resistances at the FM-SC junctions of a FM-SC-FM trilayer structure. The SC layer consists of a highly doped n++ AlGaAs GaAs 2DEG while the interfacial resistance at the FM-SC junction is modeled as delta potential (δ) barriers. The self-consistent scheme consists of a ballistic model of spin-dependent transmission across the δ barriers to evaluate RI, and a drift-diffusion model to obtain the spin-split Δμ in the electrochemical potentials. The RI values of the two junctions were found to be asymmetric despite the symmetry of the trilayer structure. This asymmetry arises from the finite biasing voltage which causes a difference in electrochemical potentials and spin accumulation at the two interfaces. The effect of RI on the spin-injection efficiency and magnetoresistance is studied over a range of δ -barrier heights. Significant spin-injection efficiency (50%) requires high δ -barrier heights approaching 1 eV. Even higher barrier heights are required to obtain equivalent magnetoresistive effect. © 2005 The American Physical Society.