Spin-injection efficiency and magnetoresistance in a hybrid ferromagnetic–semiconductor trilayer with interfacial barriers

Abstract

We present a self-consistent model of spin transport in a ferromagnetic (FM)–semiconductor (SC)–FM trilayer structure with interfacial barriers at the FM–SC boundaries. The SC layer consists of a highly doped n 2+ AlGaAs–GaAs 2DEG while the interfacial resistance is modeled as delta potential ( δ ) barriers. The self-consistent scheme combines a ballistic model of spin-dependent transmission across the δ -barriers, and a drift-diffusion model within the bulk of the trilayer. The interfacial resistance ( R I ) values of the two junctions were found to be asymmetric despite the symmetry of the trilayer structure. Transport characteristics such as the asymmetry in R I , spin-injection efficiency and magnetoresistance (MR) are calculated as a function of bulk conductivity σ s and spin-diffusion length (SDL) within the SC layer. In general a large σ s tends to improve all three characteristics, while a long SDL improves the MR ratio but reduces the spin-injection efficiency. These trends may be explained in terms of conductivity mismatch and spin accumulation either at the interfacial zones or within the bulk of the SC layer.