Spin current shown to travel over half a micrometer in a thin doped germanium film

Researchers from Japan’s Kyoto University and Osaka University have demonstrated that spin currents can travel more than half a micrometer on a thin doped-germanium sheet. Up until now this has only been demonstrated in very low temperatures (below 225 Kelvin).

Germanium has a higher electron mobility than silicon and a particular lattice symmetry that should reduce much of the electrons spin relaxation. But the material is not magnetic and so measuring spin transport is not easy because spin currents have to be created in a magnetic material and injected into germanium.

The researchers used their previously developed method for studying room-temperature spin transport in semiconductors and applied it to a germanium layer highly doped with an electron donor (phosphorous) and grown on a silicon substrate. The germanium was covered on one side by a ferromagnetic strip, excited by microwaves which was injected a spin current to the germanium. On the opposite side a metallic strip was placed and it was measured by a spin-polarization detector.

Source: APS Physics