Transistors are key components in many integrated circuits where they are used mainly as switching or amplifying devices. One of the most popular type of transistors is metal–oxide–semiconductor field-effect transistor or in short MOSFET which conventionally is consisted of a p-doped substrate and two n-doped regions known as source and drain with a gate electrode in between. Once a positive voltage applied to the gate electrode, electrons start to move from source to drain (or from drain to source when a negative voltage applied). The demand for faster, smaller and low energy consuming devices leads the research to a new generation of transistors known as spintronic transistor or spin transistor. In a spin transistor, like any other spintronic based devices the spin of electrons instead of electron themselves are used to carry the data or information. There are two main advantages of such device over the already existing transistors which are including: the ability of detecting and changing spin state without a need for an electrical current and also the permanent nature of spins which made them usable in non-volatile storage technology. As it shown in the figure, to build a spin transistor the drain and source should be replaced by ferromagnetic layers. In this case instead of moving electrons the relative rotation of spins can be used as information carrier.
An example of spin transistor is introduced by Toshiba in 2009 where a magnetic tunnel junction is used to write in magnetic layers made of full-Heusler alloy that acts as a high spin polarizer.
Categories: Advanced Topics