Electronic measurement and control of spin transport in Silicon

TL;DR

This paper demonstrates coherent spin transport in silicon over 10 microns using hot-electron filtering, overcoming previous impedance mismatch issues and parasitic effects, confirming silicon's potential for spintronic applications.

Contribution

It introduces a novel conduction band spin transport measurement method in silicon that bypasses impedance mismatch and parasitic effects, enabling clear observation of spin coherence.

Findings

Spin transport in silicon confirmed over 10 microns

Hot-electron filtering enables impedance mismatch-free spin injection/detection

Coherent spin drift demonstrated in silicon conduction band

Abstract

The electron spin lifetime and diffusion length are transport parameters that define the scale of coherence in spintronic devices and circuits. Since these parameters are many orders of magnitude larger in semiconductors than in metals, semiconductors could be the most suitable for spintronics. Thus far, spin transport has only been measured in direct-bandgap semiconductors or in combination with magnetic semiconductors, excluding a wide range of non-magnetic semiconductors with indirect bandgaps. Most notable in this group is silicon (Si), which (in addition to its market entrenchment in electronics) has long been predicted a superior semiconductor for spintronics with enhanced lifetime and diffusion length due to low spin-orbit scattering and lattice inversion symmetry. Despite its exciting promise, a demonstration of coherent spin transport in Si has remained elusive, because most experiments focused on magnetoresistive devices; these methods fail because of universal impedance mismatch obstacles, and are obscured by Lorentz magnetoresistance and Hall effects. Here we demonstrate conduction band spin transport across 10 microns undoped Si, by using spin-dependent ballistic hot-electron filtering through ferromagnetic thin films for both spin-injection and detection. Not based on magnetoresistance, the hot electron spin-injection and detection avoids impedance mismatch issues and prevents interference from parasitic effects. The clean collector current thus shows independent magnetic and electrical control of spin precession and confirms spin coherent drift in the conduction band of silicon.