Three-Terminal Device for Realizing a Voltage-Driven Spin Transistor

We propose a three-terminal device incorporating a magnetic tunnel junction (MTJ) in which the free layer magnetization can be controlled by the separated gate electrode through voltage-induced magnetic anisotropy change-in other words, a voltage-driven spin transistor. We have developed a process for fabricating a three-terminal structure in which the drain and source junctions are connected through the common free layer. The theoretical calculations allow us to discuss how to achieve high-power gain. Because the gate resistance decreases as the junction size decreases, higher power gain can be obtained with a smaller junction size. Power amplification of greater than 104 is achievable if we employ an MTJ with a resistance-area product less than 5 Ω · μm² and a junction size less than 50 nm. This three-terminal device structure for realizing a voltage-driven spin transistor represents a promising contribution to the development of high-performance spin transistors.