Spin-on transistors: make the transistors non-volatile

Spin FETs and spin MOSFETs

As a carrier of information, in addition to the original charge, there is a spin transistor that uses a spin phenomenon. Spin transistors not only make the transistor non-volatile, but also reduce switching energy. It is expected to be practical after 2020.

Previously referred to as spin transistors, mostly referred to as "spin FETs" in which the spin state of the channel is reversed by the gate electric field. In addition to being non-volatile, spin FETs can also reduce switching energy compared to existing MOSFETs. The reason is that the energy required to reverse the spin state of the channel is lower than the energy required to form the existing MOSFET channel. However, spin FETs also face many practical problems such as realizing a 0.1 to 1 μm-length channel necessary for reversing the spin state of a channel.

Referring to the spin transistors, the spin-FETs (a) that previously used the gate electric field to change the spin direction are often referred to. Recently, however, research and development of spin MOSFETs that are closer to practical use have become more active (b).

Compared with the above-mentioned components, "spin MOSFET" is favored as a more practical spin transistor. The spin MOSFET is an attempt to introduce non-volatile transistors by introducing a strong magnet into the source and drain sections of an ordinary MOSFET. Since the switching principle is basically the same as the MOSFET, the technical barrier is relatively low.

The spin MOSFET utilizes a phenomenon in which the resistance between the source and the drain of the source and the drain is parallel or anti-parallel, and the transistor is non-volatile. Although the function is similar to the combination of MOSFET and MTJ (magnetic tunnel junction) elements, "spin MOSFETs are easier to support work at low voltages" (Associate Professor Takuya Haruo of Tokyo Institute of Technology). (