Proposal for Efficient Generation of Spin-Polarized Current in Silicon

TL;DR

This paper proposes a spin-dependent resonant tunneling structure to efficiently generate spin-polarized current in silicon, utilizing a heavily doped polycrystalline Si layer to reduce barriers and focus tunneling electrons for enhanced spin polarization.

Contribution

It introduces a novel structure combining ferromagnetic metal and polycrystalline silicon to improve spin injection efficiency into silicon.

Findings

Tunneling current density can reach up to 10^8 A/m^2.

Spin polarization persists if ferromagnetic layer is thinner than the spin-diffusion length.

The structure effectively focuses tunneling electrons into resonant spin states.

Abstract

We propose a spin-dependent resonant tunneling structure to efficiently inject spin-polarized current into silicon (Si). By means of a heavily doped polycrystalline Si (Poly-Si) between the ferromagnetic metal (FM) and Si to reduce the Schottky barrier resistance, we estimated raising the tunneling current density up to $10^8$Am$^{-2}$. The small Fermi sea of the charge carriers in Si focuses the tunneling electrons to the resonant spin states within a small region of transverse momentum in the ferromagnet which creates the spin polarization of the current. Because of the large exchange splitting between the spin up and down bands, the decay of the spin current is explained in terms of scattering out of the focused beam. The spin polarization in the current survives only if the thickness of the FM-layer is smaller than the spin-diffusion length estimated from that cause.