Germanium: spin transistors just over the horizon

INAC recently made a significant advance toward using spin-orbit coupling in transistors as the result of research conducted in conjunction with CNRS Palaiseau and Jülich Research Center of Germany.

As its name indicates, spin-orbit coupling “couples” an electron’s momentum and spin. A new type of MRAM (magnetoresistive RAM) memory potentially capable of pushing back current limits could leverage spin-orbit coupling to multiply the pathways the electrical current can follow during the read and write cycles. Unfortunately, spin-orbit coupling, which makes it possible to manipulate spin, is virtually nonexistent in silicon and germanium, the materials used in today’s microelectronics. One solution is to add a metal layer to the materials to generate what is known as the Rashba effect to cause spin-orbit coupling.

Low-temperature molecular beam epitaxy was used at INAC to obtain very clean, defectless interfaces between the iron and germanium resulting in a strong Rashba effect. When a spin current is introduced, it is converted by the Rashba effect into a charge current at the interface between the materials. And, according to the reciprocity theorem, the reverse is also possible, which means that spin current could be generated, detected, and manipulated using current CMOS technology.

Contact: matthieu.jamet@cea.fr

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