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Scientific result | Spintronics

Large Spin Accumulations in Bulk Germanium by Spin-Hall Voltage

Researchers from INAC have managed to accumulate high spin densities in germanium over long distances. This result opens prospects for the production of a multi-terminal spintronic device where different spin voltages can be used as inputs for magneto-logic gates on germanium.
Published on 19 September 2017

Germanium is one of the most promising candidates for spintronic applications, due to its compatibility with silicon technology, long electron spin lifetime—even at room temperature—and optical properties matching the conventional telecommunication window.

Up to this point, spin accumulations in germanium have been generated using electrical spin injection schemes, from a ferromagnet.

Researchers from INAC have used the "spin-Hall effect" to directly produce a uniform spin current from an electric current in an n-doped germanium channel. The resulting spin accumulation is generated perpendicular to the electric current. Equivalent to a magnetization, this accumulation can be mapped using a microscopic technique based on a magneto-optical effect (Kerr).

Spin density up to 400 μm-3 an be achieved at the edge of a 100 μm wide germanium channel. The spin density in germanium decreases moderately (linearly) toward the center of the bar, compared to exponential decay in a III-V semiconductor such as gallium arsenide.

It is therefore possible to generate a spin accumulation in germanium over large distances, about 100 micrometers in this case, which is nearly 100 times more than in other semiconductors. In addition, spin-to-charge conversion in bulk germanium is preserved up to 120 K.

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