Spin injection with small ferromagnetic metal

We present a design for spin injection from a ferromagnetic (FM)-nonmagnetic (NM) bilayer into a semiconductor (SC) layer. This device consists of a left bilayer injector, the SC layer and a right bilayer collector. The FM has a much smaller cross-sectional area (A) compared to the device. This increases the spin-dependent resistance as a fraction of the total device resistance and reduces the effect of conductivity mismatch which suppresses spin-injection efficiency. The NM layer is required as a buffer to contain the spreading resistance (RSP) that arises from the discontinuity of A. With Ni80Fe20/Cu as the bilayers, and GaAs as the SC, our computation yields a spin-injection efficiency of 20% for doping density ND of 1018 cm−3, which rises to 30% for ND=1020cm-3.